Compounds based on 5,6,7,8-tetrahydrofolate.
A member of the vitamin B family that stimulates the hematopoietic system. It is present in the liver and kidney and is found in mushrooms, spinach, yeast, green leaves, and grasses (POACEAE). Folic acid is used in the treatment and prevention of folate deficiencies and megaloblastic anemia.
An enzyme that catalyzes the formation of methionine by transfer of a methyl group from 5-methyltetrahydrofolate to homocysteine. It requires a cobamide coenzyme. The enzyme can act on mono- or triglutamate derivatives. EC 2.1.1.13.
A subclass of enzymes of the transferase class that catalyze the transfer of a methyl group from one compound to another. (Dorland, 28th ed) EC 2.1.1.
Cell surface receptors that bind to and transport FOLIC ACID, 5-methyltetrahydrofolate, and a variety of folic acid derivatives. The receptors are essential for normal NEURAL TUBE development and transport folic acid via receptor-mediated endocytosis.
An FAD-dependent oxidoreductase found primarily in BACTERIA. It is specific for the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. This enzyme was formerly listed as EC 1.1.1.68 and 1.1.99.15.
An enzyme that catalyzes the transfer of a methyl group from S-ADENOSYLMETHIONINE to the 5-position of CYTOSINE residues in DNA.
A cobalt-containing coordination compound produced by intestinal micro-organisms and found also in soil and water. Higher plants do not concentrate vitamin B 12 from the soil and so are a poor source of the substance as compared with animal tissues. INTRINSIC FACTOR is important for the assimilation of vitamin B 12.
Tetrahydrofolates which are substituted by a formyl group at either the nitrogen atom in the 5 position or the nitrogen atom in the 10 position. N(5)-Formyltetrahydrofolate is leukovorin (citrovorum factor) while N(10)-formyltetrahydrofolate is an active coenzyme which functions as a carrier of the formyl group in a number of enzymatic reactions.
Physiologic methyl radical donor involved in enzymatic transmethylation reactions and present in all living organisms. It possesses anti-inflammatory activity and has been used in treatment of chronic liver disease. (From Merck, 11th ed)
A flavoprotein amine oxidoreductase that catalyzes the reversible conversion of 5-methyltetrahydrofolate to 5,10-methylenetetrahydrofolate. This enzyme was formerly classified as EC 1.1.1.171.
Derivatives of folic acid (pteroylglutamic acid). In gamma-glutamyl linkage they are found in many tissues. They are converted to folic acid by the action of pteroylpolyglutamate hydrolase or synthesized from folic acid by the action of folate polyglutamate synthetase. Synthetic pteroylpolyglutamic acids, which are in alpha-glutamyl linkage, are active in bacterial growth assays.
Addition of methyl groups. In histo-chemistry methylation is used to esterify carboxyl groups and remove sulfate groups by treating tissue sections with hot methanol in the presence of hydrochloric acid. (From Stedman, 25th ed)
Condition in which the plasma levels of homocysteine and related metabolites are elevated (>13.9 µmol/l). Hyperhomocysteinemia can be familial or acquired. Development of the acquired hyperhomocysteinemia is mostly associated with vitamins B and/or folate deficiency (e.g., PERNICIOUS ANEMIA, vitamin malabsorption). Familial hyperhomocysteinemia often results in a more severe elevation of total homocysteine and excretion into the urine, resulting in HOMOCYSTINURIA. Hyperhomocysteinemia is a risk factor for cardiovascular and neurodegenerative diseases, osteoporotic fractures and complications during pregnancy.
An enzyme that catalyzes the METHYLATION of GLYCINE using S-ADENOSYLMETHIONINE to form SARCOSINE with the concomitant production of S-ADENOSYLHOMOCYSTEINE.
5'-S-(3-Amino-3-carboxypropyl)-5'-thioadenosine. Formed from S-adenosylmethionine after transmethylation reactions.
A sulfur-containing essential L-amino acid that is important in many body functions.
A thiol-containing amino acid formed by a demethylation of METHIONINE.
Enzymes catalyzing the dehydrogenation of secondary amines, introducing a C=N double bond as the primary reaction. In some cases this is later hydrolyzed.
Enzymes that catalyze the methylation of amino acids after their incorporation into a polypeptide chain. S-Adenosyl-L-methionine acts as the methylating agent. EC 2.1.1.
A ubiquitously expressed folic acid transporter that functions via an antiporter mechanism which is coupled to the transport of organic phosphates.
An enzyme that transfers methyl groups from O(6)-methylguanine, and other methylated moieties of DNA, to a cysteine residue in itself, thus repairing alkylated DNA in a single-step reaction. EC 2.1.1.63.
A ZINC metalloenzyme that catalyzes the transfer of a methyl group from BETAINE to HOMOCYSTEINE to produce dimethylglycine and METHIONINE, respectively. This enzyme is a member of a family of ZINC-dependent METHYLTRANSFERASES that use THIOLS or selenols as methyl acceptors.
Anemia characterized by larger than normal erythrocytes, increased mean corpuscular volume (MCV) and increased mean corpuscular hemoglobin (MCH).
A nutritional condition produced by a deficiency of VITAMIN B 12 in the diet, characterized by megaloblastic anemia. Since vitamin B 12 is not present in plants, humans have obtained their supply from animal products, from multivitamin supplements in the form of pills, and as additives to food preparations. A wide variety of neuropsychiatric abnormalities is also seen in vitamin B 12 deficiency and appears to be due to an undefined defect involving myelin synthesis. (From Cecil Textbook of Medicine, 19th ed, p848)
An enzyme that catalyzes the methylation of the epsilon-amino group of lysine residues in proteins to yield epsilon mono-, di-, and trimethyllysine. EC 2.1.1.43.
Enzymes that catalyze the S-adenosyl-L-methionine-dependent methylation of ribonucleotide bases within a transfer RNA molecule. EC 2.1.1.
A group of water-soluble vitamins, some of which are COENZYMES.
An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA.
Enzymes that catalyze the methylation of arginine residues of proteins to yield N-mono- and N,N-dimethylarginine. This enzyme is found in many organs, primarily brain and spleen.
A nutritional condition produced by a deficiency of FOLIC ACID in the diet. Many plant and animal tissues contain folic acid, abundant in green leafy vegetables, yeast, liver, and mushrooms but destroyed by long-term cooking. Alcohol interferes with its intermediate metabolism and absorption. Folic acid deficiency may develop in long-term anticonvulsant therapy or with use of oral contraceptives. This deficiency causes anemia, macrocytic anemia, and megaloblastic anemia. It is indistinguishable from vitamin B 12 deficiency in peripheral blood and bone marrow findings, but the neurologic lesions seen in B 12 deficiency do not occur. (Merck Manual, 16th ed)
Injectable form of VITAMIN B 12 that has been used therapeutically to treat VITAMIN B 12 DEFICIENCY.
Cyclic TETRAPYRROLES based on the corrin skeleton.
Methylases that are specific for CYTOSINE residues found on DNA.
The active metabolite of FOLIC ACID. Leucovorin is used principally as an antidote to FOLIC ACID ANTAGONISTS.
A PROTEIN O-METHYLTRANSFERASE that recognizes and catalyzes the methyl esterification of ISOASPARTIC ACID and D-ASPARTIC ACID residues in peptides and proteins. It initiates the repair of proteins damaged by the spontaneous decomposition of normal L-aspartic acid and L-asparagine residues.
Enzymes that are part of the restriction-modification systems. They are responsible for producing a species-characteristic methylation pattern, on either adenine or cytosine residues, in a specific short base sequence in the host cell's own DNA. This methylated sequence will occur many times in the host-cell DNA and remain intact for the lifetime of the cell. Any DNA from another species which gains entry into a living cell and lacks the characteristic methylation pattern will be recognized by the restriction endonucleases of similar specificity and destroyed by cleavage. Most have been studied in bacterial systems, but a few have been found in eukaryotic organisms.
Leukemia L1210 is a designation for a specific murine (mouse) leukemia cell line that was originally isolated from a female mouse with an induced acute myeloid leukemia, which is widely used as a model in cancer research, particularly for in vivo studies of drug efficacy and resistance.
An enzyme responsible for producing a species-characteristic methylation pattern on adenine residues in a specific short base sequence in the host cell DNA. The enzyme catalyzes the methylation of DNA adenine in the presence of S-adenosyl-L-methionine to form DNA containing 6-methylaminopurine and S-adenosyl-L-homocysteine. EC 2.1.1.72.
A naturally occurring compound that has been of interest for its role in osmoregulation. As a drug, betaine hydrochloride has been used as a source of hydrochloric acid in the treatment of hypochlorhydria. Betaine has also been used in the treatment of liver disorders, for hyperkalemia, for homocystinuria, and for gastrointestinal disturbances. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1341)
Inhibitors of the enzyme, dihydrofolate reductase (TETRAHYDROFOLATE DEHYDROGENASE), which converts dihydrofolate (FH2) to tetrahydrofolate (FH4). They are frequently used in cancer chemotherapy. (From AMA, Drug Evaluations Annual, 1994, p2033)
Addition of methyl groups to DNA. DNA methyltransferases (DNA methylases) perform this reaction using S-ADENOSYLMETHIONINE as the methyl group donor.
A multifunctional pyridoxal phosphate enzyme. In the second stage of cysteine biosynthesis it catalyzes the reaction of homocysteine with serine to form cystathionine with the elimination of water. Deficiency of this enzyme leads to HYPERHOMOCYSTEINEMIA and HOMOCYSTINURIA. EC 4.2.1.22.
Compounds based on 2-amino-4-hydroxypteridine.
Homocysteine is an non-proteinaceous α-amino acid, with the formula (SCH2)2NCH2CO2H, which is formed during methionine metabolism and is a key intermediate in the transmethylation and transsulfuration pathways; elevated levels of homocysteine in the blood are associated with several disease conditions.
A peptide that is a homopolymer of glutamic acid.
Products in capsule, tablet or liquid form that provide dietary ingredients, and that are intended to be taken by mouth to increase the intake of nutrients. Dietary supplements can include macronutrients, such as proteins, carbohydrates, and fats; and/or MICRONUTRIENTS, such as VITAMINS; MINERALS; and PHYTOCHEMICALS.
A subtype of GPI-anchored folate receptors that is expressed in tissues of epithelial origin. This protein is also identified as an ovarian-tumor-specific antigen.
A symporter protein that couples the transport of FOLIC ACID with HYDROGEN IONS. The transporter functions most effectively under acidic conditions.
Nitrogen oxide (N2O). A colorless, odorless gas that is used as an anesthetic and analgesic. High concentrations cause a narcotic effect and may replace oxygen, causing death by asphyxia. It is also used as a food aerosol in the preparation of whipping cream.
Transport proteins that carry specific substances in the blood or across cell membranes.
Compounds based on pyrazino[2,3-d]pyrimidine which is a pyrimidine fused to a pyrazine, containing four NITROGEN atoms.
Catalyzes the hydrolysis of pteroylpolyglutamic acids in gamma linkage to pterolylmonoglutamic acid and free glutamic acid. EC 3.4.19.9.
The rate dynamics in chemical or physical systems.
Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.
A genus of motile or nonmotile gram-positive bacteria of the family Clostridiaceae. Many species have been identified with some being pathogenic. They occur in water, soil, and in the intestinal tract of humans and lower animals.
An enzyme that catalyzes the conversion of methylmalonyl-CoA to succinyl-CoA by transfer of the carbonyl group. It requires a cobamide coenzyme. A block in this enzymatic conversion leads to the metabolic disease, methylmalonic aciduria. EC 5.4.99.2.
VITAMIN B 6 refers to several PICOLINES (especially PYRIDOXINE; PYRIDOXAL; & PYRIDOXAMINE) that are efficiently converted by the body to PYRIDOXAL PHOSPHATE which is a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, and aminolevulinic acid. During transamination of amino acids, pyridoxal phosphate is transiently converted into PYRIDOXAMINE phosphate. Although pyridoxine and Vitamin B 6 are still frequently used as synonyms, especially by medical researchers, this practice is erroneous and sometimes misleading (EE Snell; Ann NY Acad Sci, vol 585 pg 1, 1990). Most of vitamin B6 is eventually degraded to PYRIDOXIC ACID and excreted in the urine.
The extent to which the active ingredient of a drug dosage form becomes available at the site of drug action or in a biological medium believed to reflect accessibility to a site of action.
The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.
Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.
Congenital malformations of the central nervous system and adjacent structures related to defective neural tube closure during the first trimester of pregnancy generally occurring between days 18-29 of gestation. Ectodermal and mesodermal malformations (mainly involving the skull and vertebrae) may occur as a result of defects of neural tube closure. (From Joynt, Clinical Neurology, 1992, Ch55, pp31-41)
A megaloblastic anemia occurring in children but more commonly in later life, characterized by histamine-fast achlorhydria, in which the laboratory and clinical manifestations are based on malabsorption of vitamin B 12 due to a failure of the gastric mucosa to secrete adequate and potent intrinsic factor. (Dorland, 27th ed)
A natural product that has been considered as a growth factor for some insects.
Cystathionine is an intermediate sulfur-containing amino acid in the transsulfuration pathway, formed from homocysteine and serine by the enzyme cystathionine beta-synthase, which is involved in the biosynthesis of cysteine and glutathione.
A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.
An enzyme that catalyses three sequential METHYLATION reactions for conversion of phosphatidylethanolamine to PHOSPHATIDYLCHOLINE.
Small chromosomal proteins (approx 12-20 kD) possessing an open, unfolded structure and attached to the DNA in cell nuclei by ionic linkages. Classification into the various types (designated histone I, histone II, etc.) is based on the relative amounts of arginine and lysine in each.
The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.
An enzyme that catalyzes the transfer of methyl groups from S-adenosylmethionine to free carboxyl groups of a protein molecule forming methyl esters. EC 2.1.1.-.
This enzyme catalyzes the last step of CREATINE biosynthesis by catalyzing the METHYLATION of guanidinoacetate to CREATINE.
An enzyme that catalyzes the METHYLATION of phosphatidyl-N-methylethanolamine to produce phosphatidyl-N-dimethylethanolamine. This enzyme can also methylate phosphatidyl-N-dimethylethanolamine to produce phosphatidyl-N-trimethylethanolamine (PHOSPHATIDYLCHOLINE).
An enzyme that catalyzes the demethylation of L-homocysteine to L-METHIONINE.
Autosomal recessive inborn error of methionine metabolism usually caused by a deficiency of CYSTATHIONINE BETA-SYNTHASE and associated with elevations of homocysteine in plasma and urine. Clinical features include a tall slender habitus, SCOLIOSIS, arachnodactyly, MUSCLE WEAKNESS, genu varus, thin blond hair, malar flush, lens dislocations, an increased incidence of MENTAL RETARDATION, and a tendency to develop fibrosis of arteries, frequently complicated by CEREBROVASCULAR ACCIDENTS and MYOCARDIAL INFARCTION. (From Adams et al., Principles of Neurology, 6th ed, p979)
Acetyl CoA participates in the biosynthesis of fatty acids and sterols, in the oxidation of fatty acids and in the metabolism of many amino acids. It also acts as a biological acetylating agent.
The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.
Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.
A pyrimidine analogue that inhibits DNA methyltransferase, impairing DNA methylation. It is also an antimetabolite of cytidine, incorporated primarily into RNA. Azacytidine has been used as an antineoplastic agent.
The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.
Derivatives of GLUTAMIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the 2-aminopentanedioic acid structure.
An individual in which both alleles at a given locus are identical.
A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.
A species of halophilic archaea whose organisms are nonmotile. Habitats include freshwater and marine mud, animal-waste lagoons, and the rumens of ungulates.
A multisubunit polycomb protein complex that catalyzes the METHYLATION of chromosomal HISTONE H3. It works in conjunction with POLYCOMB REPRESSIVE COMPLEX 1 to effect EPIGENETIC REPRESSION.
An enzyme of the oxidoreductase class that catalyzes the reaction 7,8-dihyrofolate and NADPH to yield 5,6,7,8-tetrahydrofolate and NADPH+, producing reduced folate for amino acid metabolism, purine ring synthesis, and the formation of deoxythymidine monophosphate. Methotrexate and other folic acid antagonists used as chemotherapeutic drugs act by inhibiting this enzyme. (Dorland, 27th ed) EC 1.5.1.3.
The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.
Membrane proteins whose primary function is to facilitate the transport of molecules across a biological membrane. Included in this broad category are proteins involved in active transport (BIOLOGICAL TRANSPORT, ACTIVE), facilitated transport and ION CHANNELS.
The white liquid secreted by the mammary glands. It contains proteins, sugar, lipids, vitamins, and minerals.
A malonic acid derivative which is a vital intermediate in the metabolism of fat and protein. Abnormalities in methylmalonic acid metabolism lead to methylmalonic aciduria. This metabolic disease is attributed to a block in the enzymatic conversion of methylmalonyl CoA to succinyl CoA.
Established cell cultures that have the potential to propagate indefinitely.
Tritium is an isotope of hydrogen (specifically, hydrogen-3) that contains one proton and two neutrons in its nucleus, making it radioactive with a half-life of about 12.3 years, and is used in various applications including nuclear research, illumination, and dating techniques due to its low energy beta decay.
Stable carbon atoms that have the same atomic number as the element carbon, but differ in atomic weight. C-13 is a stable carbon isotope.
An essential amino acid. It is often added to animal feed.
A genetic process by which the adult organism is realized via mechanisms that lead to the restriction in the possible fates of cells, eventually leading to their differentiated state. Mechanisms involved cause heritable changes to cells without changes to DNA sequence such as DNA METHYLATION; HISTONE modification; DNA REPLICATION TIMING; NUCLEOSOME positioning; and heterochromatization which result in selective gene expression or repression.
A pyrimidine base that is a fundamental unit of nucleic acids.
Interruption or suppression of the expression of a gene at transcriptional or translational levels.
A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).
Elements of limited time intervals, contributing to particular results or situations.
The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
Chromatography on non-ionic gels without regard to the mechanism of solute discrimination.
Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.
A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.
A thiol-containing non-essential amino acid that is oxidized to form CYSTINE.
The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)
A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment.
A mass spectrometry technique using two (MS/MS) or more mass analyzers. With two in tandem, the precursor ions are mass-selected by a first mass analyzer, and focused into a collision region where they are then fragmented into product ions which are then characterized by a second mass analyzer. A variety of techniques are used to separate the compounds, ionize them, and introduce them to the first mass analyzer. For example, for in GC-MS/MS, GAS CHROMATOGRAPHY-MASS SPECTROMETRY is involved in separating relatively small compounds by GAS CHROMATOGRAPHY prior to injecting them into an ionization chamber for the mass selection.
DNA sequences which are recognized (directly or indirectly) and bound by a DNA-dependent RNA polymerase during the initiation of transcription. Highly conserved sequences within the promoter include the Pribnow box in bacteria and the TATA BOX in eukaryotes.
An enzyme which catalyzes the catabolism of S-ADENOSYLHOMOCYSTEINE to ADENOSINE and HOMOCYSTEINE. It may play a role in regulating the concentration of intracellular adenosylhomocysteine.
The 4-methanol form of VITAMIN B 6 which is converted to PYRIDOXAL PHOSPHATE which is a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, aminolevulinic acid. Although pyridoxine and Vitamin B 6 are still frequently used as synonyms, especially by medical researchers, this practice is erroneous and sometimes misleading (EE Snell; Ann NY Acad Sci, vol 585 pg 1, 1990).
Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.
Areas of increased density of the dinucleotide sequence cytosine--phosphate diester--guanine. They form stretches of DNA several hundred to several thousand base pairs long. In humans there are about 45,000 CpG islands, mostly found at the 5' ends of genes. They are unmethylated except for those on the inactive X chromosome and some associated with imprinted genes.
Highly reactive compounds produced when oxygen is reduced by a single electron. In biological systems, they may be generated during the normal catalytic function of a number of enzymes and during the oxidation of hemoglobin to METHEMOGLOBIN. In living organisms, SUPEROXIDE DISMUTASE protects the cell from the deleterious effects of superoxides.
The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.
The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.
Nucleic acid structures found on the 5' end of eukaryotic cellular and viral messenger RNA and some heterogeneous nuclear RNAs. These structures, which are positively charged, protect the above specified RNAs at their termini against attack by phosphatases and other nucleases and promote mRNA function at the level of initiation of translation. Analogs of the RNA caps (RNA CAP ANALOGS), which lack the positive charge, inhibit the initiation of protein synthesis.
The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.
A vitamin found in green vegetables. It is used in the treatment of peptic ulcers, colitis, and gastritis and has an effect on secretory, acid-forming, and enzymatic functions of the intestinal tract.
An amino acid intermediate in the metabolism of choline.
The level of protein structure in which combinations of secondary protein structures (alpha helices, beta sheets, loop regions, and motifs) pack together to form folded shapes called domains. Disulfide bridges between cysteines in two different parts of the polypeptide chain along with other interactions between the chains play a role in the formation and stabilization of tertiary structure. Small proteins usually consist of only one domain but larger proteins may contain a number of domains connected by segments of polypeptide chain which lack regular secondary structure.
An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.
Proteins which maintain the transcriptional quiescence of specific GENES or OPERONS. Classical repressor proteins are DNA-binding proteins that are normally bound to the OPERATOR REGION of an operon, or the ENHANCER SEQUENCES of a gene until a signal occurs that causes their release.
An antineoplastic agent. It has significant activity against melanomas. (from Martindale, The Extra Pharmacopoeia, 31st ed, p564)
A class of drugs that differs from other alkylating agents used clinically in that they are monofunctional and thus unable to cross-link cellular macromolecules. Among their common properties are a requirement for metabolic activation to intermediates with antitumor efficacy and the presence in their chemical structures of N-methyl groups, that after metabolism, can covalently modify cellular DNA. The precise mechanisms by which each of these drugs acts to kill tumor cells are not completely understood. (From AMA, Drug Evaluations Annual, 1994, p2026)
Myeloid-lymphoid leukemia protein is a transcription factor that maintains high levels of HOMEOTIC GENE expression during development. The GENE for myeloid-lymphoid leukemia protein is commonly disrupted in LEUKEMIA and combines with over 40 partner genes to form FUSION ONCOGENE PROTEINS.
Guanine is a purine nucleobase, one of the four nucleobases in the nucleic acid of DNA and RNA, involved in forming hydrogen bonds between complementary base pairs in double-stranded DNA molecules.
The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.
The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.
A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).
The parts of a macromolecule that directly participate in its specific combination with another molecule.
A condition due to deficiency in any member of the VITAMIN B COMPLEX. These B vitamins are water-soluble and must be obtained from the diet because they are easily lost in the urine. Unlike the lipid-soluble vitamins, they cannot be stored in the body fat.
A group of carrier proteins which bind with VITAMIN B12 in the BLOOD and aid in its transport. Transcobalamin I migrates electrophoretically as a beta-globulin, while transcobalamins II and III migrate as alpha-globulins.
Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control of gene action in enzyme synthesis.
The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.
Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.
An ASPARTIC ACID residue in polypeptide chains that is linked at the beta-carboxyl group instead of at the normal, alpha-carboxyl group, polypeptide linkage. It is a result of the spontaneous decomposition of aspartic acid or ASPARAGINE residues.
The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.
RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.
The material of CHROMOSOMES. It is a complex of DNA; HISTONES; and nonhistone proteins (CHROMOSOMAL PROTEINS, NON-HISTONE) found within the nucleus of a cell.
A nutritional condition produced by a deficiency of VITAMIN B 6 in the diet, characterized by dermatitis, glossitis, cheilosis, and stomatitis. Marked deficiency causes irritability, weakness, depression, dizziness, peripheral neuropathy, and seizures. In infants and children typical manifestations are diarrhea, anemia, and seizures. Deficiency can be caused by certain medications, such as isoniazid.
A hydrocarbon used as an industrial solvent. It has been used as an aerosal propellent, as a refrigerant and as a local anesthetic. (From Martindale, The Extra Pharmacopoeia, 31st ed, p1403)
An antibiotic purine ribonucleoside that readily substitutes for adenosine in the biological system, but its incorporation into DNA and RNA has an inhibitory effect on the metabolism of these nucleic acids.
A methylated nucleotide base found in eukaryotic DNA. In ANIMALS, the DNA METHYLATION of CYTOSINE to form 5-methylcytosine is found primarily in the palindromic sequence CpG. In PLANTS, the methylated sequence is CpNpGp, where N can be any base.

Folate and homocysteine metabolism in copper-deficient rats. (1/254)

To investigate the effect of copper deficiency on folate and homocysteine metabolism, we measured plasma, red-cell and hepatic folate, plasma homocysteine and vitamin B-12 concentrations, and hepatic methionine synthase activities in rats. Two groups of male Sprague-Dawley rats were fed semi-purified diets containing either 0. 1 mg (copper-deficient group) or 9.2 mg (control group) of copper per kg. After 6 weeks of dietary treatment, copper deficiency was established as evidenced by markedly decreased plasma and hepatic copper concentrations in rats fed the low-copper diet. Plasma, red-cell, hepatic folate, and plasma vitamin B-12 concentrations were similar in both groups, whereas plasma homocysteine concentrations in the copper-deficient group were significantly higher than in the control group (P<0.05). Copper deficiency resulted in a 21% reduction in hepatic methionine synthase activity as compared to the control group (P<0.01). This change most likely caused the increased hepatic 5-methyltetrahydrofolate and plasma homocysteine concentrations in the copper-deficient group. Our results indicate that hepatic methionine synthase may be a cuproenzyme, and plasma homocysteine concentrations are influenced by copper nutriture in rats. These data support the concept that copper deficiency can be a risk factor for cardiovascular disease.  (+info)

Co-ordinate variations in methylmalonyl-CoA mutase and methionine synthase, and the cobalamin cofactors in human glioma cells during nitrous oxide exposure and the subsequent recovery phase. (2/254)

We investigated the co-ordinate variations of the two cobalamin (Cbl)-dependent enzymes, methionine synthase (MS) and methylmalonyl-CoA mutase (MCM), and measured the levels of their respective cofactors, methylcobalamin (CH3Cbl) and adenosylcobalamin (AdoCbl) in cultured human glioma cells during nitrous oxide exposure and during a subsequent recovery period of culture in a nitrous oxide-free atmosphere (air). In agreement with published data, MS as the primary target of nitrous oxide was inactivated rapidly (initial rate of 0.06 h(-1)), followed by reduction of CH3Cbl (to <20%). Both enzyme activity and cofactor levels recovered rapidly when the cells were subsequently cultured in air, but the recovery was completely blocked by the protein-synthesis inhibitor, cycloheximide. During MS inactivation, there was a reduction of cellular AdoCbl and holo-MCM activity (measured in the absence of exogenous AdoCbl) to about 50% of pre-treatment levels. When the cells were transferred to air, both AdoCbl and holo-MCM activity recovered, albeit more slowly than the MS system. Notably, the regain of the holo-MCM and AdoCbl was enhanced rather than inhibited by cycloheximide. These findings confirm irreversible damage of MS by nitrous oxide; hence, synthesis of the enzyme is required to restore its activity. In contrast, restoration of holo-MCM activity is only dependent on repletion of the AdoCbl cofactor. We also observed a synchronous fluctuation in AdoCbl and the much larger hydroxycobalamin pool during the inactivation and recovery phase, suggesting that the loss and repletion of AdoCbl reflect changes in intracellular Cbl homoeostasis. Our data demonstrate that the nitrous oxide-induced changes in MS and CH3Cbl are associated with reversible changes in both MCM holoactivity and the AdoCbl level, suggesting co-ordinate distribution of Cbl cofactors during depletion and repletion.  (+info)

Reversal of ethanol-induced hepatic steatosis and lipid peroxidation by taurine: a study in rats. (3/254)

Alcohol (ethanol) was administered chronically to female Sprague-Dawley rats in a nutritionally adequate, totally liquid diet for 28 days. This resulted in significant hepatic steatosis and lipid peroxidation. When taurine was administered for 2 days following alcohol withdrawal it was found to reduce alcohol-induced lipid peroxidation and completely reversed hepatic steatosis. The reversal of hepatic steatosis was demonstrated both biochemically and histologically. Two days following alcohol withdrawal, the apparent activity of the alcohol-inducible form of cytochrome P450 (CYP2E1) was unchanged although total cytochrome P450 content was increased. In addition, alcohol significantly inhibited hepatic methionine synthase activity and increased homocysteine excretion in urine. Although alcohol did not affect the urinary excretion of taurine (a non-invasive marker of liver damage), levels of serum and hepatic taurine were markedly raised in animals given taurine following their treatment with alcohol, compared to animals given taurine alone. There was evidence of slight bile duct injury in animals treated with alcohol and with alcohol followed by taurine, as indicated by raised serum alkaline phosphatase (ALP) and cholesterol. Aspartate aminotransferase (AST) was also slightly raised. The effects of taurine on reversing hepatic steatosis may be due to the enhanced secretion of hepatic triglycerides. It is suggested that increased bile flow as a result of taurine treatment may have contributed to the removal of lipid peroxides. These in-vivo findings demonstrate for the first time that hepatic steatosis and lipid peroxidation, occurring as a result of chronic alcohol consumption, can be reversed by administration of taurine to rats for 2 days.  (+info)

A new class of cobalamin transport mutants (btuF) provides genetic evidence for a periplasmic binding protein in Salmonella typhimurium. (4/254)

No periplasmic binding protein has been demonstrated for the ATP-binding cassette (ABC)-type cobalamin transporter BtuCD. New mutations (btuF) are described that affect inner-membrane transport. The BtuF protein has a signal sequence and resembles the periplasmic binding proteins of several other ABC transporters.  (+info)

Molecular basis for methionine synthase reductase deficiency in patients belonging to the cblE complementation group of disorders in folate/cobalamin metabolism. (5/254)

Methionine synthase reductase (MSR) deficiency is an autosomal recessive disorder of folate/cobalamin metabolism leading to hyperhomocysteinemia, hypo- methioninemia and megaloblastic anemia. Deficiency in MSR activity occurs as the result of a defect in the MSR enzyme, which is required for the reductive activation of methionine synthase (MS). MS itself is responsible for the folate/cobalamin-dependent conversion of homo- cysteine to methionine. We have recently cloned the cDNA corresponding to the MSR protein, a novel member of the ferredoxin-NADP(+)reductase (FNR) family of electron transferases. We have used RT-PCR, heteroduplex, single-strand conformation poly- morphism (SSCP) and DNA sequence analyses to reveal 11 mutations in eight patients from seven families belonging to the cblE complementation group of patients of cobalamin metabolism that is defective in the MSR protein. The mutations include splicing defects leading to large insertions or deletions, as well as a number of smaller deletions and point mutations. Apart from an intronic substitution found in two unrelated patients, the mutations appear singular among individuals. Of the eleven, three are nonsense mutations, allowing for the identification of two patients for whom little if any MSR protein should be produced. The remaining eight involve point mutations or in-frame disruptions of the coding sequence and are distributed throughout the coding region, including proposed FMN, FAD and NADPH binding sites. These data demonstrate a unique requirement for MSR in the reductive activation of MS.  (+info)

A polymorphism of the methionine synthase gene: association with plasma folate, vitamin B12, homocyst(e)ine, and colorectal cancer risk. (6/254)

We previously reported (J. Chen et al., Cancer Res., 56: 4862-4864, 1996; J. Ma et al., Cancer Res., 57: 1098-1102, 1997) that a 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphism (677C-->T, ala-->val) was associated with lower risk of colorectal cancer. In this study, we examined the relationship of a polymorphism (2756A-->G, asp-->gly) in the gene (MTR) for methionine synthase, another important enzyme in the same folate/methionine/homocyst(e)ine metabolic pathway, with risk of colorectal cancer among 356 cases and 476 cancer-free controls. The frequency of the homozygous variant genotype (gly/gly) was slightly lower among cases (3%) than controls (5%). The odds ratio for the gly/gly genotype was 0.59 [95% confidence interval (CI), 0.27-1.27] compared with those with the homozygous wild type (asp/asp). There were no significant differences in plasma levels of folate, vitamin B12, and homocyst(e)ine (tHcy) among the MTR genotypes, in contrast to the MTHFR polymorphism. However, similar to the interaction observed for the MTHFR polymorphism among men who consumed less than 1 alcoholic drink/day, those with the gly/gly genotype had a lower risk of colorectal cancer with an odds ratio of 0.27 (95% CI, 0.09-0.81) compared with those with the asp/asp genotype. The possible association of the MTR polymorphism with lower risk of colorectal cancer especially among those with low alcohol consumption, in the same direction as for the MTHFR polymorphism, is intriguing. However, our study had limited statistical power because of the low frequency of the MTR variant genotype, which is reflected in the wide CIs. Hence, these findings need to be confirmed in larger populations.  (+info)

Heterologous high level expression, purification, and enzymological properties of recombinant rat cobalamin-dependent methionine synthase. (7/254)

Rat methionine synthase was expressed chiefly as apoenzyme in recombinant baculovirus-infected insect cells (Yamada, K., Tobimatsu, T., and Toraya, T. (1998) Biosci. Biotech. Biochem. 62, 2155-2160). The apoenzyme produced was very unstable, and therefore, after complexation with methylcobalamin, the functional holoenzyme was purified to homogeneity. The specific activity and apparent K(m) values for substrates were in good agreement with those obtained with purified rat liver enzyme. The electronic spectrum of the purified recombinant enzyme resembled that of cob(II)alamin and changed to a methylcobalamin-like one upon incubation of the enzyme with titanium(III) and S-adenosylmethionine. The rate of oxidative inactivation of the enzyme in the absence of S-adenosylmethionine was slower with a stronger reducing agent like titanium(III). The nucleotide moiety, especially the phosphodiester group, was shown to play an important role in the binding of the coenzyme to apoprotein and thus for catalysis. Upon incubation with the apoenzyme in the absence of a reducing agent, cyano- and aquacobalamin were not effective or were effective only slightly in reconstituting holoenzyme. Ethyl- and propylcobalamin formed inactive complexes with apoenzyme, which were converted to holoenzyme by photolytic activation. Adenosylcobalamin was not able to form a complex with apoenzyme, which was convertible to holoenzyme by photoirradiation.  (+info)

Characterization and functional expression of cDNAs encoding methionine-sensitive and -insensitive homocysteine S-methyltransferases from Arabidopsis. (8/254)

Plants synthesize S-methylmethionine (SMM) from S-adenosylmethionine (AdoMet), and methionine (Met) by a unique reaction and, like other organisms, use SMM as a methyl donor for Met synthesis from homocysteine (Hcy). These reactions comprise the SMM cycle. Two Arabidopsis cDNAs specifying enzymes that mediate the SMM --> Met reaction (SMM:Hcy S-methyltransferase, HMT) were identified by homology and authenticated by complementing an Escherichia coli yagD mutant and by detecting HMT activity in complemented cells. Gel blot analyses indicate that these enzymes, AtHMT-1 and -2, are encoded by single copy genes. The deduced polypeptides are similar in size (36 kDa), share a zinc-binding motif, lack obvious targeting sequences, and are 55% identical to each other. The recombinant enzymes exist as monomers. AtHMT-1 and -2 both utilize l-SMM or (S,S)-AdoMet as a methyl donor in vitro and have higher affinities for SMM. Both enzymes also use either methyl donor in vivo because both restore the ability to utilize AdoMet or SMM to a yeast HMT mutant. However, AtHMT-1 is strongly inhibited by Met, whereas AtHMT-2 is not, a difference that could be crucial to the control of flux through the HMT reaction and the SMM cycle. Plant HMT is known to transfer the pro-R methyl group of SMM. This enabled us to use recombinant AtHMT-1 to establish that the other enzyme of the SMM cycle, AdoMet:Met S-methyltransferase, introduces the pro-S methyl group. These opposing stereoselectivities suggest a way to measure in vivo flux through the SMM cycle.  (+info)

Tetrahydrofolates (THFs) are a type of folate, which is a form of vitamin B9. Folate is essential for the production and maintenance of new cells, especially in DNA synthesis and methylation. THFs are the active forms of folate in the body and are involved in various metabolic processes, including:

1. The conversion of homocysteine to methionine, an amino acid required for protein synthesis and the formation of S-adenosylmethionine (SAM), a major methyl donor in the body.
2. The transfer of one-carbon units in various metabolic reactions, such as the synthesis of purines and pyrimidines, which are essential components of DNA and RNA.
3. The remethylation of homocysteine to methionine, a process that helps maintain normal homocysteine levels in the body. Elevated homocysteine levels have been linked to an increased risk of cardiovascular disease.

THFs can be obtained from dietary sources, such as leafy green vegetables, legumes, and fortified cereals. They can also be synthesized endogenously in the body through the action of the enzyme dihydrofolate reductase (DHFR), which reduces dihydrofolate (DHF) to THF using NADPH as a cofactor.

Deficiencies in folate or impaired THF metabolism can lead to various health issues, including megaloblastic anemia, neural tube defects during fetal development, and an increased risk of cardiovascular disease due to elevated homocysteine levels.

Folic acid is the synthetic form of folate, a type of B vitamin (B9). It is widely used in dietary supplements and fortified foods because it is more stable and has a longer shelf life than folate. Folate is essential for normal cell growth and metabolism, and it plays a critical role in the formation of DNA and RNA, the body's genetic material. Folic acid is also crucial during early pregnancy to prevent birth defects of the brain and spine called neural tube defects.

Medical Definition: "Folic acid is the synthetic form of folate (vitamin B9), a water-soluble vitamin involved in DNA synthesis, repair, and methylation. It is used in dietary supplementation and food fortification due to its stability and longer shelf life compared to folate. Folic acid is critical for normal cell growth, development, and red blood cell production."

5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase is also known as Methionine Synthase. It is a vital enzyme in the human body that plays a crucial role in methionine metabolism and homocysteine regulation.

The medical definition of 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase is as follows:

A enzyme (EC 2.1.1.13) that catalyzes the methylation of homocysteine to methionine, using 5-methyltetrahydrofolate as a methyl donor. This reaction also requires the cofactor vitamin B12 (cobalamin) as a coenzyme. The enzyme is located in the cytosol of cells and is essential for the synthesis of methionine, which is an important amino acid required for various biological processes such as protein synthesis, methylation reactions, and the formation of neurotransmitters.

Deficiency or dysfunction of this enzyme can lead to several health issues, including homocystinuria, a genetic disorder characterized by elevated levels of homocysteine in the blood, which can cause serious complications such as neurological damage, cardiovascular disease, and skeletal abnormalities.

Methyltransferases are a class of enzymes that catalyze the transfer of a methyl group (-CH3) from a donor molecule to an acceptor molecule, which is often a protein, DNA, or RNA. This transfer of a methyl group can modify the chemical and physical properties of the acceptor molecule, playing a crucial role in various cellular processes such as gene expression, signal transduction, and DNA repair.

In biochemistry, methyltransferases are classified based on the type of donor molecule they use for the transfer of the methyl group. The most common methyl donor is S-adenosylmethionine (SAM), a universal methyl group donor found in many organisms. Methyltransferases that utilize SAM as a cofactor are called SAM-dependent methyltransferases.

Abnormal regulation or function of methyltransferases has been implicated in several diseases, including cancer and neurological disorders. Therefore, understanding the structure, function, and regulation of these enzymes is essential for developing targeted therapies to treat these conditions.

Folate receptors (FRs) are a group of cell surface proteins that bind and transport folate (vitamin B9) into cells. The subtype referred to as "GPI-anchored" refers to the type of anchoring that these receptors have in the cell membrane.

GPI stands for glycosylphosphatidylinositol, which is a molecule that acts as an anchor for certain proteins in the cell membrane. GPI-anchored folate receptors are attached to the outer layer of the cell membrane through this GPI anchor, rather than being embedded within the membrane like many other proteins.

GPI-anchored folate receptors are found on various types of cells, including some cancer cells, and they play a role in the uptake of folate into those cells. Folate is an essential nutrient that plays a critical role in DNA synthesis and methylation, among other processes. Abnormalities in folate metabolism have been linked to various diseases, including cancer and neurological disorders.

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a crucial role in the synthesis of DNA, formation of red blood cells, and maintenance of the nervous system. It is involved in the metabolism of every cell in the body, particularly affecting DNA regulation and neurological function.

Vitamin B12 is unique among vitamins because it contains a metal ion, cobalt, from which its name is derived. This vitamin can be synthesized only by certain types of bacteria and is not produced by plants or animals. The major sources of vitamin B12 in the human diet include animal-derived foods such as meat, fish, poultry, eggs, and dairy products, as well as fortified plant-based milk alternatives and breakfast cereals.

Deficiency in vitamin B12 can lead to various health issues, including megaloblastic anemia, fatigue, neurological symptoms such as numbness and tingling in the extremities, memory loss, and depression. Since vitamin B12 is not readily available from plant-based sources, vegetarians and vegans are at a higher risk of deficiency and may require supplementation or fortified foods to meet their daily requirements.

Formyltetrahydrofolates are a type of folate coenzyme that plays a crucial role in the metabolism of amino acids and nucleotides. They are formed from tetrahydrofolate, a reduced form of folic acid, by the addition of a one-carbon unit in the form of a formyl group (CHO). This process is catalyzed by the enzyme formyltetrahydrofolate synthetase.

Formyltetrahydrofolates are involved in several important metabolic pathways, including the synthesis of purines and pyrimidines, which are essential components of DNA and RNA. They also play a role in the methionine cycle, which is involved in the synthesis of various essential molecules such as neurotransmitters, phospholipids, and methyl groups required for DNA methylation.

Deficiencies in formyltetrahydrofolates or their precursors can lead to a variety of health problems, including megaloblastic anemia, neural tube defects, and cardiovascular disease. Therefore, it is important to ensure adequate intake of folate-rich foods or supplements, especially during pregnancy and in individuals with certain genetic polymorphisms that affect folate metabolism.

S-Adenosylmethionine (SAMe) is a physiological compound involved in methylation reactions, transulfuration pathways, and aminopropylation processes in the body. It is formed from the coupling of methionine, an essential sulfur-containing amino acid, and adenosine triphosphate (ATP) through the action of methionine adenosyltransferase enzymes.

SAMe serves as a major methyl donor in various biochemical reactions, contributing to the synthesis of numerous compounds such as neurotransmitters, proteins, phospholipids, nucleic acids, and other methylated metabolites. Additionally, SAMe plays a crucial role in the detoxification process within the liver by participating in glutathione production, which is an important antioxidant and detoxifying agent.

In clinical settings, SAMe supplementation has been explored as a potential therapeutic intervention for various conditions, including depression, osteoarthritis, liver diseases, and fibromyalgia, among others. However, its efficacy remains a subject of ongoing research and debate within the medical community.

Pteroylpolyglutamic acids are forms of folic acid that are composed of multiple glutamic acid molecules linked together in a chain. This compound is also known as polyglutamated folate or folylpolyglutamates. The length of the glutamic acid chain can vary, and these compounds are often found naturally in foods such as leafy green vegetables, fruits, and dried beans.

In the body, pteroylpolyglutamic acids must be converted to the active form of folate, called tetrahydrofolate, before they can participate in various metabolic processes, including DNA synthesis and methylation reactions. Some people may have difficulty absorbing or converting these compounds due to genetic factors or certain medical conditions, which can lead to folate deficiency and related health problems.

It's worth noting that supplemental forms of folic acid are typically in the form of a single glutamate molecule (pteroylmonoglutamic acid) and may not be as effective at raising folate levels in the body as the polyglutamated forms found in food. However, the monoglutamate form is more easily absorbed and utilized by the body, making it a common choice for supplementation.

Methylation, in the context of genetics and epigenetics, refers to the addition of a methyl group (CH3) to a molecule, usually to the nitrogenous base of DNA or to the side chain of amino acids in proteins. In DNA methylation, this process typically occurs at the 5-carbon position of cytosine residues that precede guanine residues (CpG sites) and is catalyzed by enzymes called DNA methyltransferases (DNMTs).

DNA methylation plays a crucial role in regulating gene expression, genomic imprinting, X-chromosome inactivation, and suppression of repetitive elements. Hypermethylation or hypomethylation of specific genes can lead to altered gene expression patterns, which have been associated with various human diseases, including cancer.

In summary, methylation is a fundamental epigenetic modification that influences genomic stability, gene regulation, and cellular function by introducing methyl groups to DNA or proteins.

Hyperhomocysteinemia is a medical condition characterized by an excessively high level of homocysteine, an amino acid, in the blood. Generally, a level of 15 micromoles per liter (μmol/L) or higher is considered elevated.

Homocysteine is a byproduct of methionine metabolism, an essential amino acid obtained from dietary proteins. Normally, homocysteine gets converted back to methionine with the help of vitamin B12 and folate (vitamin B9), or it can be converted to another amino acid, cysteine, with the aid of vitamin B6.

Hyperhomocysteinemia can occur due to genetic defects in these enzymes, nutritional deficiencies of vitamins B12, B6, or folate, renal insufficiency, or aging. High homocysteine levels are associated with increased risks of cardiovascular diseases, including atherosclerosis, thrombosis, and stroke. It may also contribute to neurodegenerative disorders like Alzheimer's disease and cognitive decline.

It is essential to diagnose and manage hyperhomocysteinemia early to prevent potential complications. Treatment typically involves dietary modifications, supplementation of the deficient vitamins, and, in some cases, medication.

Glycine N-Methyltransferase (GNMT) is an enzyme that plays a crucial role in methionine and homocysteine metabolism. It is primarily found in the liver and to some extent in the kidneys, pancreas, and brain.

GNMT catalyzes the transfer of a methyl group from S-adenosylmethionine (SAM) to glycine, forming S-adenosylhomocysteine (SAH) and sarcosine as products. This reaction helps regulate the levels of SAM, SAH, and homocysteine in the body.

Additionally, GNMT has been shown to have other functions, such as detoxification of xenobiotics and regulation of lipid metabolism. Abnormal GNMT activity or expression has been linked to various diseases, including liver disorders, cardiovascular disease, and cancer.

S-Adenosylhomocysteine (SAH) is a metabolic byproduct formed from the demethylation of various compounds or from the breakdown of S-adenosylmethionine (SAM), which is a major methyl group donor in the body. SAH is rapidly hydrolyzed to homocysteine and adenosine by the enzyme S-adenosylhomocysteine hydrolase. Increased levels of SAH can inhibit many methyltransferases, leading to disturbances in cellular metabolism and potential negative health effects.

Methionine is an essential amino acid, which means that it cannot be synthesized by the human body and must be obtained through the diet. It plays a crucial role in various biological processes, including:

1. Protein synthesis: Methionine is one of the building blocks of proteins, helping to create new proteins and maintain the structure and function of cells.
2. Methylation: Methionine serves as a methyl group donor in various biochemical reactions, which are essential for DNA synthesis, gene regulation, and neurotransmitter production.
3. Antioxidant defense: Methionine can be converted to cysteine, which is involved in the formation of glutathione, a potent antioxidant that helps protect cells from oxidative damage.
4. Homocysteine metabolism: Methionine is involved in the conversion of homocysteine back to methionine through a process called remethylation, which is essential for maintaining normal homocysteine levels and preventing cardiovascular disease.
5. Fat metabolism: Methionine helps facilitate the breakdown and metabolism of fats in the body.

Foods rich in methionine include meat, fish, dairy products, eggs, and some nuts and seeds.

Homocysteine is an amino acid that is formed in the body during the metabolism of another amino acid called methionine. It's an important intermediate in various biochemical reactions, including the synthesis of proteins, neurotransmitters, and other molecules. However, elevated levels of homocysteine in the blood (a condition known as hyperhomocysteinemia) have been linked to several health issues, such as cardiovascular disease, stroke, and cognitive decline.

Homocysteine can be converted back to methionine with the help of vitamin B12 and a cofactor called betaine, or it can be converted to another amino acid called cystathionine with the help of vitamin B6 and folate (vitamin B9). Imbalances in these vitamins and other factors can lead to an increase in homocysteine levels.

It is crucial to maintain normal homocysteine levels for overall health, as high levels may contribute to the development of various diseases. Regular monitoring and maintaining a balanced diet rich in folate, vitamin B6, and vitamin B12 can help regulate homocysteine levels and reduce the risk of related health issues.

Oxidoreductases acting on CH-NH group donors are a class of enzymes within the larger group of oxidoreductases, which are responsible for catalyzing oxidation-reduction reactions. Specifically, this subclass of enzymes acts on CH-NH group donors, where the CH-NH group is a chemical functional group consisting of a carbon atom (C) bonded to a nitrogen atom (N) via a single covalent bond.

These enzymes play a crucial role in various biological processes by transferring electrons from the CH-NH group donor to an acceptor molecule, which results in the oxidation of the donor and reduction of the acceptor. This process can lead to the formation or breakdown of chemical bonds, and plays a key role in metabolic pathways such as amino acid degradation and nitrogen fixation.

Examples of enzymes that fall within this class include:

* Amino oxidases, which catalyze the oxidative deamination of amino acids to produce alpha-keto acids, ammonia, and hydrogen peroxide.
* Transaminases, which transfer an amino group from one molecule to another, often in the process of amino acid biosynthesis or degradation.
* Amine oxidoreductases, which catalyze the oxidation of primary amines to aldehydes and secondary amines to ketones, with the concomitant reduction of molecular oxygen to hydrogen peroxide.

Protein methyltransferases (PMTs) are a family of enzymes that transfer methyl groups from a donor, such as S-adenosylmethionine (SAM), to specific residues on protein substrates. This post-translational modification plays a crucial role in various cellular processes, including epigenetic regulation, signal transduction, and protein stability.

PMTs can methylate different amino acid residues, such as lysine, arginine, and histidine, on proteins. The methylation of these residues can lead to changes in the charge, hydrophobicity, or interaction properties of the target protein, thereby modulating its function.

For example, lysine methyltransferases (KMTs) are a subclass of PMTs that specifically methylate lysine residues on histone proteins, which are the core components of nucleosomes in chromatin. Histone methylation can either activate or repress gene transcription, depending on the specific residue and degree of methylation.

Protein arginine methyltransferases (PRMTs) are another subclass of PMTs that methylate arginine residues on various protein substrates, including histones, transcription factors, and RNA-binding proteins. Arginine methylation can also affect protein function by altering its interaction with other molecules or modulating its stability.

Overall, protein methyltransferases are essential regulators of cellular processes and have been implicated in various diseases, including cancer, neurodegenerative disorders, and cardiovascular diseases. Therefore, understanding the mechanisms and functions of PMTs is crucial for developing novel therapeutic strategies to target these diseases.

The Reduced Folate Carrier Protein (RFC) is also known as the Folate Receptor Alpha (FR-α). It is a transmembrane protein responsible for the cellular influx of reduced folates, which are essential cofactors in various metabolic processes, particularly DNA synthesis and methylation. These processes are vital for cell growth, division, and development.

Reduced Folate Carrier Protein is widely expressed in many tissues, including the kidneys, liver, intestines, and choroid plexus. It plays a crucial role in maintaining intracellular folate homeostasis by facilitating the uptake of reduced folates from circulation into cells.

Dysfunctions or mutations in the RFC gene can lead to impaired folate transport, which may result in various clinical manifestations, such as megaloblastic anemia and neurological disorders. Proper folate status is essential for overall health, particularly during pregnancy and fetal development, as it helps prevent neural tube defects in newborns.

Betaine-Homocysteine S-Methyltransferase (BHMT) is an enzyme that catalyzes the methylation of homocysteine to methionine using betaine as a methyl donor. This reaction plays a crucial role in maintaining the homeostasis of methionine and homocysteine, which are important for various biological processes such as methylation reactions, protein synthesis, and neurotransmitter production.

The BHMT enzyme is primarily found in the liver and kidneys, where it helps to regulate the levels of homocysteine in the body. Elevated levels of homocysteine have been linked to several health issues, including cardiovascular disease, neurological disorders, and bone diseases. Therefore, BHMT plays an essential role in maintaining overall health by regulating homocysteine metabolism.

Macrocytic anemia is a type of anemia in which the red blood cells are larger than normal in size (macrocytic). This condition can be caused by various factors such as deficiency of vitamin B12 or folate, alcohol abuse, certain medications, bone marrow disorders, and some inherited genetic conditions.

The large red blood cells may not function properly, leading to symptoms such as fatigue, weakness, shortness of breath, pale skin, and a rapid heartbeat. Macrocytic anemia can be diagnosed through a complete blood count (CBC) test, which measures the size and number of red blood cells in the blood.

Treatment for macrocytic anemia depends on the underlying cause. In cases of vitamin B12 or folate deficiency, supplements or dietary changes may be recommended. If the anemia is caused by medication, a different medication may be prescribed. In severe cases, blood transfusions or injections of vitamin B12 may be necessary.

Vitamin B12 deficiency is a condition characterized by insufficient levels of vitamin B12 in the body, leading to impaired production of red blood cells, nerve function damage, and potential neurological complications. Vitamin B12 is an essential nutrient that plays a crucial role in DNA synthesis, fatty acid metabolism, and maintaining the health of the nervous system.

The medical definition of vitamin B12 deficiency includes:

1. Reduced serum or whole blood vitamin B12 concentrations (typically below 200 pg/mL or 145 pmol/L)
2. Presence of clinical symptoms and signs, such as:
* Fatigue, weakness, and lethargy
* Pale skin, shortness of breath, and heart palpitations due to anemia (megaloblastic or macrocytic anemia)
* Neurological symptoms like numbness, tingling, or burning sensations in the hands and feet (peripheral neuropathy), balance problems, confusion, memory loss, and depression
3. Laboratory findings consistent with deficiency, such as:
* Increased mean corpuscular volume (MCV) of red blood cells
* Reduced numbers of red and white blood cells and platelets in severe cases
* Elevated homocysteine and methylmalonic acid levels in the blood due to impaired metabolism

The most common causes of vitamin B12 deficiency include dietary insufficiency (common in vegetarians and vegans), pernicious anemia (an autoimmune condition affecting intrinsic factor production), gastrointestinal disorders (such as celiac disease, Crohn's disease, or gastric bypass surgery), and certain medications that interfere with vitamin B12 absorption.

Untreated vitamin B12 deficiency can lead to severe complications, including irreversible nerve damage, cognitive impairment, and increased risk of cardiovascular diseases. Therefore, prompt diagnosis and treatment are essential for preventing long-term health consequences.

Histone-Lysine N-Methyltransferase is a type of enzyme that transfers methyl groups to specific lysine residues on histone proteins. These histone proteins are the main protein components of chromatin, which is the complex of DNA and proteins that make up chromosomes.

Histone-Lysine N-Methyltransferases play a crucial role in the regulation of gene expression by modifying the structure of chromatin. The addition of methyl groups to histones can result in either the activation or repression of gene transcription, depending on the specific location and number of methyl groups added.

These enzymes are important targets for drug development, as their dysregulation has been implicated in various diseases, including cancer. Inhibitors of Histone-Lysine N-Methyltransferases have shown promise in preclinical studies for the treatment of certain types of cancer.

tRNA (transfer RNA) methyltransferases are a group of enzymes that catalyze the transfer of a methyl group (-CH3) to specific positions on the tRNA molecule. These enzymes play a crucial role in modifying and regulating tRNA function, stability, and interaction with other components of the translation machinery during protein synthesis.

The addition of methyl groups to tRNAs can occur at various sites, including the base moieties of nucleotides within the anticodon loop, the TψC loop, and the variable region. These modifications help maintain the structural integrity of tRNA molecules, enhance their ability to recognize specific codons during translation, and protect them from degradation by cellular nucleases.

tRNA methyltransferases are classified based on the type of methylation they catalyze:

1. N1-methyladenosine (m1A) methyltransferases: These enzymes add a methyl group to the N1 position of adenosine residues in tRNAs. An example is TRMT6/TRMT61A, which methylates adenosines at position 58 in human tRNAs.
2. N3-methylcytosine (m3C) methyltransferases: These enzymes add a methyl group to the N3 position of cytosine residues in tRNAs. An example is Dnmt2, which methylates cytosines at position 38 in various organisms.
3. N7-methylguanosine (m7G) methyltransferases: These enzymes add a methyl group to the N7 position of guanosine residues in tRNAs, primarily at position 46 within the TψC loop. An example is Trm8/Trm82, which catalyzes this modification in yeast and humans.
4. 2'-O-methylated nucleotides (Nm) methyltransferases: These enzymes add a methyl group to the 2'-hydroxyl group of ribose sugars in tRNAs, which can occur at various positions throughout the molecule. An example is FTSJ1, which methylates uridines at position 8 in human tRNAs.
5. Pseudouridine (Ψ) synthases: Although not technically methyltransferases, pseudouridine synthases catalyze the isomerization of uridine to pseudouridine, which can enhance tRNA stability and function. An example is Dyskerin (DKC1), which introduces Ψ at various positions in human tRNAs.

These enzymes play crucial roles in modifying tRNAs, ensuring proper folding, stability, and function during translation. Defects in these enzymes can lead to various diseases, including neurological disorders, cancer, and premature aging.

Vitamin B Complex refers to a group of water-soluble vitamins that play essential roles in cell metabolism, cellular function, and formation of red blood cells. This complex includes 8 distinct vitamins, all of which were originally thought to be the same vitamin when first discovered. They are now known to have individual structures and specific functions.

1. Vitamin B1 (Thiamin): Necessary for energy production and nerve function.
2. Vitamin B2 (Riboflavin): Involved in energy production and growth.
3. Vitamin B3 (Niacin): Assists in energy production, DNA repair, and acts as a co-factor for various enzymes.
4. Vitamin B5 (Pantothenic Acid): Plays a role in the synthesis of Coenzyme A, which is vital for fatty acid metabolism.
5. Vitamin B6 (Pyridoxine): Needed for protein metabolism, neurotransmitter synthesis, hemoglobin formation, and immune function.
6. Vitamin B7 (Biotin): Involved in fatty acid synthesis, glucose metabolism, and nail and hair health.
7. Vitamin B9 (Folate or Folic Acid): Essential for DNA replication, cell division, and the production of red blood cells.
8. Vitamin B12 (Cobalamin): Necessary for nerve function, DNA synthesis, and the production of red blood cells.

These vitamins are often found together in various foods, and a balanced diet usually provides sufficient amounts of each. Deficiencies can lead to specific health issues related to the functions of each particular vitamin.

Methotrexate is a medication used in the treatment of certain types of cancer and autoimmune diseases. It is an antimetabolite that inhibits the enzyme dihydrofolate reductase, which is necessary for the synthesis of purines and pyrimidines, essential components of DNA and RNA. By blocking this enzyme, methotrexate interferes with cell division and growth, making it effective in treating rapidly dividing cells such as cancer cells.

In addition to its use in cancer treatment, methotrexate is also used to manage autoimmune diseases such as rheumatoid arthritis, psoriasis, and inflammatory bowel disease. In these conditions, methotrexate modulates the immune system and reduces inflammation.

It's important to note that methotrexate can have significant side effects and should be used under the close supervision of a healthcare provider. Regular monitoring of blood counts, liver function, and kidney function is necessary during treatment with methotrexate.

Protein-Arginine N-Methyltransferases (PRMTs) are a group of enzymes that catalyze the transfer of methyl groups from S-adenosylmethionine to specific arginine residues in proteins, leading to the formation of N-methylarginines. This post-translational modification plays a crucial role in various cellular processes such as signal transduction, DNA repair, and RNA processing. There are nine known PRMTs in humans, which can be classified into three types based on the type of methylarginine produced: Type I (PRMT1, 2, 3, 4, 6, and 8) produce asymmetric dimethylarginines, Type II (PRMT5 and 9) produce symmetric dimethylarginines, and Type III (PRMT7) produces monomethylarginine. Aberrant PRMT activity has been implicated in several diseases, including cancer and neurological disorders.

Folic Acid Deficiency is a condition characterized by insufficient levels of folic acid (Vitamin B9) in the body. Folic acid plays an essential role in the synthesis of DNA and RNA, the production of red blood cells, and the prevention of neural tube defects during fetal development.

A deficiency in folic acid can lead to a variety of health issues, including:
- Megaloblastic anemia: A type of anemia characterized by large, structurally abnormal, immature red blood cells (megaloblasts) that are unable to function properly. This results in fatigue, weakness, shortness of breath, and a pale appearance.
- Neural tube defects: In pregnant women, folic acid deficiency can increase the risk of neural tube defects, such as spina bifida and anencephaly, in the developing fetus.
- Developmental delays and neurological disorders: In infants and children, folic acid deficiency during pregnancy can lead to developmental delays, learning difficulties, and neurological disorders.
- Increased risk of cardiovascular disease: Folate plays a role in maintaining healthy homocysteine levels. Deficiency can result in elevated homocysteine levels, which is an independent risk factor for cardiovascular disease.

Folic acid deficiency can be caused by various factors, including poor dietary intake, malabsorption syndromes (such as celiac disease or Crohn's disease), pregnancy, alcoholism, certain medications (like methotrexate and phenytoin), and genetic disorders affecting folate metabolism. To prevent or treat folic acid deficiency, dietary supplementation with folic acid is often recommended, especially for pregnant women and individuals at risk of deficiency.

Hydroxocobalamin is a form of vitamin B12 that is used in medical treatments. It is a synthetic version of the naturally occurring compound, and it is often used to treat vitamin B12 deficiencies. Hydroxocobalamin is also used to treat poisoning from cyanide, as it can bind with the cyanide to form a non-toxic compound that can be excreted from the body.

In medical terms, hydroxocobalamin is defined as: "A bright red crystalline compound, C21H30CoN4O7·2H2O, used in the treatment of vitamin B12 deficiency and as an antidote for cyanide poisoning. It is converted in the body to active coenzyme forms."

It's important to note that hydroxocobalamin should only be used under the supervision of a medical professional, as improper use can lead to serious side effects or harm.

Corrinoids are a class of compounds that include vitamin B12 and its analogs. Vitamin B12 is an essential nutrient for humans and other animals, playing a critical role in the synthesis of DNA, the maintenance of the nervous system, and the metabolism of fatty acids and amino acids.

The corrinoid ring is the structural backbone of vitamin B12 and its analogs. It is a complex, planar molecule made up of four pyrrole rings joined together in a macrocycle. The corrinoid ring contains a central cobalt ion, which can form coordination bonds with various ligands, including organic groups such as methyl, hydroxo, and cyano.

Corrinoids can be found in a wide variety of foods, including meat, dairy products, fish, eggs, and some fortified plant-based foods. They are also produced by certain bacteria, which can synthesize the corrinoid ring and the cobalt ion de novo. Some corrinoids have biological activity similar to vitamin B12, while others do not.

In addition to their role in human nutrition, corrinoids are also used in industrial applications, such as the production of antibiotics and other pharmaceuticals. They are also used as catalysts in chemical reactions, due to their ability to form stable coordination complexes with various ligands.

DNA cytosine methylases are a type of enzyme that catalyze the transfer of a methyl group (-CH3) to the carbon-5 position of the cytosine ring in DNA, forming 5-methylcytosine. This process is known as DNA methylation and plays an important role in regulating gene expression, genomic imprinting, X-chromosome inactivation, and suppression of transposable elements in eukaryotic organisms.

In mammals, the most well-studied DNA cytosine methylases are members of the DNMT (DNA methyltransferase) family, including DNMT1, DNMT3A, and DNMT3B. DNMT1 is primarily responsible for maintaining existing methylation patterns during DNA replication, while DNMT3A and DNMT3B are involved in establishing new methylation patterns during development and differentiation.

Abnormal DNA methylation patterns have been implicated in various diseases, including cancer, where global hypomethylation and promoter-specific hypermethylation can contribute to genomic instability, chromosomal aberrations, and silencing of tumor suppressor genes.

Leucovorin is the pharmaceutical name for a form of folic acid, also known as folinic acid. It is used in medicine as a medication to reduce the toxic effects of certain chemotherapy drugs, such as methotrexate, that work by blocking the action of folic acid in the body. Leucovorin is able to bypass this blockage and restore some of the necessary functions of folic acid, helping to prevent or reduce the severity of side effects like nausea, vomiting, and damage to the mucous membranes.

Leucovorin may also be used in combination with fluorouracil chemotherapy to enhance its effectiveness in treating certain types of cancer. It is important to note that leucovorin should only be used under the supervision of a healthcare professional, as it can interact with other medications and have potentially serious side effects if not used properly.

Protein D-aspartate-L-isoaspartate methyltransferase (PCMT or PRMT5) is an enzyme that catalyzes the transfer of a methyl group from S-adenosylmethionine to the side chain nitrogen atom of a specific aspartate or glutamate residue on protein substrates. This enzyme plays a crucial role in the maintenance of protein structure and function by correcting the spontaneous deamidation of asparagine and isomerization of aspartate to isoaspartate residues, which can lead to protein aggregation and loss of function. PCMT also regulates various cellular processes, including transcription, RNA processing, DNA damage repair, and signal transduction, by modifying the activity or localization of its target proteins.

DNA modification methylases are a type of enzyme that catalyze the transfer of methyl groups (-CH3) to specific nucleotides in DNA, usually cytosine or adenine residues. This process is known as DNA methylation and is an important epigenetic mechanism that regulates gene expression, genome stability, and other cellular processes.

There are several types of DNA modification methylases, including:

1. Cytosine-5 methyltransferases (CNMTs or DNMTs): These enzymes catalyze the transfer of a methyl group to the fifth carbon atom of cytosine residues in DNA, forming 5-methylcytosine (5mC). This is the most common type of DNA methylation and plays a crucial role in gene silencing, X-chromosome inactivation, and genomic imprinting.
2. N6-adenine methyltransferases (MTases): These enzymes catalyze the transfer of a methyl group to the sixth nitrogen atom of adenine residues in DNA, forming N6-methyladenine (6mA). This type of DNA methylation is less common than 5mC but has been found to be involved in various cellular processes, such as transcriptional regulation and DNA repair.
3. GpC methyltransferases: These enzymes catalyze the transfer of a methyl group to the second carbon atom of guanine residues in DNA, forming N4-methylcytosine (4mC). This type of DNA methylation is relatively rare and has been found mainly in prokaryotic genomes.

Dysregulation of DNA modification methylases has been implicated in various diseases, including cancer, neurological disorders, and immunological diseases. Therefore, understanding the function and regulation of these enzymes is essential for developing novel therapeutic strategies to treat these conditions.

Leukemia L1210 is not a medical definition itself, but it refers to a specific mouse leukemia cell line that was established in 1948. These cells are a type of acute myeloid leukemia (AML) and have been widely used in cancer research as a model for studying the disease, testing new therapies, and understanding the biology of leukemia. The L1210 cell line has contributed significantly to the development of various chemotherapeutic agents and treatment strategies for leukemia and other cancers.

Betaine, also known as trimethylglycine, is a naturally occurring compound that can be found in various foods such as beets, spinach, and whole grains. In the body, betaine functions as an osmolyte, helping to regulate water balance in cells, and as a methyl donor, contributing to various metabolic processes including the conversion of homocysteine to methionine.

In medical terms, betaine is also used as a dietary supplement and medication. Betaine hydrochloride is a form of betaine that is sometimes used as a supplement to help with digestion by providing additional stomach acid. Betaine anhydrous, on the other hand, is often used as a supplement for improving athletic performance and promoting liver health.

Betaine has also been studied for its potential role in protecting against various diseases, including cardiovascular disease, diabetes, and neurological disorders. However, more research is needed to fully understand its mechanisms of action and therapeutic potential.

Folic acid antagonists are a class of medications that work by inhibiting the action of folic acid or its metabolic pathways. These drugs are commonly used in the treatment of various types of cancer and certain other conditions, such as rheumatoid arthritis. They include drugs such as methotrexate, pemetrexed, and trimetrexate.

Folic acid is a type of B vitamin that is essential for the production of DNA and RNA, the genetic material found in cells. Folic acid antagonists work by interfering with the enzyme responsible for converting folic acid into its active form, tetrahydrofolate. This interference prevents the formation of new DNA and RNA, which is necessary for cell division and growth. As a result, these drugs can inhibit the proliferation of rapidly dividing cells, such as cancer cells.

It's important to note that folic acid antagonists can also affect normal, non-cancerous cells in the body, particularly those that divide quickly, such as cells in the bone marrow and digestive tract. This can lead to side effects such as anemia, mouth sores, and diarrhea. Therefore, these drugs must be used carefully and under the close supervision of a healthcare provider.

DNA methylation is a process by which methyl groups (-CH3) are added to the cytosine ring of DNA molecules, often at the 5' position of cytospine phosphate-deoxyguanosine (CpG) dinucleotides. This modification is catalyzed by DNA methyltransferase enzymes and results in the formation of 5-methylcytosine.

DNA methylation plays a crucial role in the regulation of gene expression, genomic imprinting, X chromosome inactivation, and suppression of transposable elements. Abnormal DNA methylation patterns have been associated with various diseases, including cancer, where tumor suppressor genes are often silenced by promoter methylation.

In summary, DNA methylation is a fundamental epigenetic modification that influences gene expression and genome stability, and its dysregulation has important implications for human health and disease.

Cystathionine beta-synthase (CBS) is an enzyme that plays a crucial role in the metabolic pathway responsible for the production of the amino acid cysteine from homocysteine. CBS catalyzes the condensation of serine with homocysteine to form cystathionine, which is subsequently hydrolyzed to cysteine and alpha-ketobutyrate by another enzyme called cystathionine gamma-lyase.

CBS requires the cofactor pyridoxal 5'-phosphate (PLP) for its activity and is primarily located in the liver, where it helps regulate homocysteine levels in the body. Elevated levels of homocysteine have been linked to various health issues, including cardiovascular disease and neurological disorders.

In addition to its role in cysteine synthesis, CBS also contributes to the transsulfuration pathway, which is involved in the detoxification of methionine and the production of glutathione, an essential antioxidant in the body. Genetic mutations in the CBS gene can lead to conditions such as homocystinuria, a rare inherited metabolic disorder characterized by elevated levels of homocysteine and methionine in the blood and urine.

Pterins are a group of naturally occurring pigments that are derived from purines. They are widely distributed in various organisms, including bacteria, fungi, and animals. In humans, pterins are primarily found in the eye, skin, and hair. Some pterins have been found to play important roles as cofactors in enzymatic reactions and as electron carriers in metabolic pathways.

Abnormal levels of certain pterins can be indicative of genetic disorders or other medical conditions. For example, an excess of biopterin, a type of pterin, is associated with phenylketonuria (PKU), a genetic disorder that affects the body's ability to metabolize the amino acid phenylalanine. Similarly, low levels of neopterin, another type of pterin, can be indicative of immune system dysfunction or certain types of cancer.

Medical professionals may measure pterin levels in blood, urine, or other bodily fluids to help diagnose and monitor these conditions.

Homocysteine is an amino acid that is formed from the metabolism of another amino acid called methionine. It is not normally present in significant amounts in the diet, but it can be elevated in some people due to genetic factors or nutritional deficiencies (such as a lack of vitamin B12, folate, or betaine). Elevated levels of homocysteine in the blood have been linked to an increased risk of cardiovascular disease, including heart attack and stroke. Homocysteine can be converted back to methionine through a process that requires the presence of vitamin B12, folate, and betaine. It can also be converted to another amino acid called cystathionine through a reaction that requires the enzyme cystathionine beta-synthase and the cofactor vitamin B6.

Polyglutamic acid (PGA) is not a medical term per se, but it is a term used in biochemistry and cosmetics. Medically, it may be mentioned in the context of certain medical conditions or treatments. Here's a definition:

Polyglutamic acid is a polymer of glutamic acid, a type of amino acid. It is a natural substance found in various foods such as natto, a traditional Japanese fermented soybean dish. In the human body, it is produced by certain bacteria during fermentation processes.

PGA has been studied for its potential medical applications due to its unique properties, including its ability to retain moisture and form gels. It has been explored as a wound dressing material, drug delivery vehicle, and anti-aging cosmetic ingredient. However, it is not a widely used or recognized medical treatment at this time.

A dietary supplement is a product that contains nutrients, such as vitamins, minerals, amino acids, herbs or other botanicals, and is intended to be taken by mouth, to supplement the diet. Dietary supplements can include a wide range of products, such as vitamin and mineral supplements, herbal supplements, and sports nutrition products.

Dietary supplements are not intended to treat, diagnose, cure, or alleviate the effects of diseases. They are intended to be used as a way to add extra nutrients to the diet or to support specific health functions. It is important to note that dietary supplements are not subject to the same rigorous testing and regulations as drugs, so it is important to choose products carefully and consult with a healthcare provider if you have any questions or concerns about using them.

Folate Receptor 1 (FR-α or FOLR1) is a protein that is encoded by the folate receptor 1 gene in humans. It is a member of the folate receptor family, which are responsible for the transport of folate (vitamin B9) into cells. FR-α is primarily expressed in the epithelial cells of various organs, including the lungs, kidneys, and choroid plexus.

FR-α has a high affinity for folic acid and reduced folates, which it internalizes through receptor-mediated endocytosis. Once inside the cell, these molecules are converted to tetrahydrofolate (THF), an essential cofactor in various metabolic processes such as DNA synthesis, repair, and methylation.

In addition to its physiological role, FR-α has been implicated in several pathological conditions, including cancer. Many tumors, particularly ovarian and lung cancers, overexpress FR-α, making it an attractive target for targeted therapy using folate-conjugated drugs or radiolabeled folic acid for imaging and treatment.

The Proton-Coupled Folate Transporter (PCFT), also known as SLC46A1, is a membrane protein responsible for the absorption and transport of folate across the intestinal epithelium and other cell types. It functions by coupling the movement of protons (H+) with the transport of folate ions against their concentration gradient, which allows for the accumulation of folate inside the cells. PCFT plays a crucial role in folate homeostasis and has been identified as a potential therapeutic target in cancer treatment due to its overexpression in certain tumors.

Nitrous oxide, also known as laughing gas, is a colorless and non-flammable gas with a slightly sweet odor and taste. In medicine, it's commonly used for its anesthetic and pain reducing effects. It is often used in dental procedures, surgery, and childbirth to help reduce anxiety and provide mild sedation. Nitrous oxide works by binding to the hemoglobin in red blood cells, which reduces the oxygen-carrying capacity of the blood, but this effect is usually not significant at the low concentrations used for analgesia and anxiolysis. It's also considered relatively safe when administered by a trained medical professional because it does not cause depression of the respiratory system or cardiovascular function.

Carrier proteins, also known as transport proteins, are a type of protein that facilitates the movement of molecules across cell membranes. They are responsible for the selective and active transport of ions, sugars, amino acids, and other molecules from one side of the membrane to the other, against their concentration gradient. This process requires energy, usually in the form of ATP (adenosine triphosphate).

Carrier proteins have a specific binding site for the molecule they transport, and undergo conformational changes upon binding, which allows them to move the molecule across the membrane. Once the molecule has been transported, the carrier protein returns to its original conformation, ready to bind and transport another molecule.

Carrier proteins play a crucial role in maintaining the balance of ions and other molecules inside and outside of cells, and are essential for many physiological processes, including nerve impulse transmission, muscle contraction, and nutrient uptake.

Pteridines are a class of heterocyclic aromatic organic compounds that are structurally related to pterins, which contain a pyrimidine ring fused to a pyrazine ring. They are naturally occurring substances that can be found in various living organisms such as bacteria, fungi, plants, and animals.

Pteridines have several important biological functions. For instance, they play a crucial role in the synthesis of folate and biotin, which are essential cofactors for various metabolic reactions in the body. Additionally, some pteridines function as chromophores, contributing to the coloration of certain organisms such as butterflies and birds.

In medicine, pteridines have been studied for their potential therapeutic applications. For example, some synthetic pteridine derivatives have shown promising results in preclinical studies as antitumor, antiviral, and antibacterial agents. However, further research is needed to fully understand the medical implications of these compounds.

Gamma-glutamyl hydrolase (GGH) is an enzyme that plays a role in the metabolism of certain amino acids, specifically glutathione and its related compounds. Glutathione is a tripeptide consisting of cysteine, glutamic acid, and glycine, and it functions as an important antioxidant in the body.

GGH catalyzes the hydrolysis of the gamma-glutamyl bond in glutathione and its related compounds, releasing free glutamate and a dipeptide. This reaction is an essential step in the recycling of these amino acids and the synthesis of new glutathione molecules.

A deficiency in GGH activity has been associated with several diseases, including neurodegenerative disorders and cancer. Inhibitors of GGH have also been investigated as potential therapeutic agents for the treatment of certain cancers, as they may help to reduce the levels of glutathione and enhance the effectiveness of chemotherapy drugs.

In the context of medicine and pharmacology, "kinetics" refers to the study of how a drug moves throughout the body, including its absorption, distribution, metabolism, and excretion (often abbreviated as ADME). This field is called "pharmacokinetics."

1. Absorption: This is the process of a drug moving from its site of administration into the bloodstream. Factors such as the route of administration (e.g., oral, intravenous, etc.), formulation, and individual physiological differences can affect absorption.

2. Distribution: Once a drug is in the bloodstream, it gets distributed throughout the body to various tissues and organs. This process is influenced by factors like blood flow, protein binding, and lipid solubility of the drug.

3. Metabolism: Drugs are often chemically modified in the body, typically in the liver, through processes known as metabolism. These changes can lead to the formation of active or inactive metabolites, which may then be further distributed, excreted, or undergo additional metabolic transformations.

4. Excretion: This is the process by which drugs and their metabolites are eliminated from the body, primarily through the kidneys (urine) and the liver (bile).

Understanding the kinetics of a drug is crucial for determining its optimal dosing regimen, potential interactions with other medications or foods, and any necessary adjustments for special populations like pediatric or geriatric patients, or those with impaired renal or hepatic function.

Cell surface receptors, also known as membrane receptors, are proteins located on the cell membrane that bind to specific molecules outside the cell, known as ligands. These receptors play a crucial role in signal transduction, which is the process of converting an extracellular signal into an intracellular response.

Cell surface receptors can be classified into several categories based on their structure and mechanism of action, including:

1. Ion channel receptors: These receptors contain a pore that opens to allow ions to flow across the cell membrane when they bind to their ligands. This ion flux can directly activate or inhibit various cellular processes.
2. G protein-coupled receptors (GPCRs): These receptors consist of seven transmembrane domains and are associated with heterotrimeric G proteins that modulate intracellular signaling pathways upon ligand binding.
3. Enzyme-linked receptors: These receptors possess an intrinsic enzymatic activity or are linked to an enzyme, which becomes activated when the receptor binds to its ligand. This activation can lead to the initiation of various signaling cascades within the cell.
4. Receptor tyrosine kinases (RTKs): These receptors contain intracellular tyrosine kinase domains that become activated upon ligand binding, leading to the phosphorylation and activation of downstream signaling molecules.
5. Integrins: These receptors are transmembrane proteins that mediate cell-cell or cell-matrix interactions by binding to extracellular matrix proteins or counter-receptors on adjacent cells. They play essential roles in cell adhesion, migration, and survival.

Cell surface receptors are involved in various physiological processes, including neurotransmission, hormone signaling, immune response, and cell growth and differentiation. Dysregulation of these receptors can contribute to the development of numerous diseases, such as cancer, diabetes, and neurological disorders.

'Clostridium' is a genus of gram-positive, rod-shaped bacteria that are widely distributed in nature, including in soil, water, and the gastrointestinal tracts of animals and humans. Many species of Clostridium are anaerobic, meaning they can grow and reproduce in environments with little or no oxygen. Some species of Clostridium are capable of producing toxins that can cause serious and sometimes life-threatening illnesses in humans and animals.

Some notable species of Clostridium include:

* Clostridium tetani, which causes tetanus (also known as lockjaw)
* Clostridium botulinum, which produces botulinum toxin, the most potent neurotoxin known and the cause of botulism
* Clostridium difficile, which can cause severe diarrhea and colitis, particularly in people who have recently taken antibiotics
* Clostridium perfringens, which can cause food poisoning and gas gangrene.

It is important to note that not all species of Clostridium are harmful, and some are even beneficial, such as those used in the production of certain fermented foods like sauerkraut and natto. However, due to their ability to produce toxins and cause illness, it is important to handle and dispose of materials contaminated with Clostridium species carefully, especially in healthcare settings.

Methylmalonyl-CoA mutase is a mitochondrial enzyme that plays a crucial role in the metabolism of certain amino acids and fatty acids. Specifically, it catalyzes the isomerization of methylmalonyl-CoA to succinyl-CoA, which is an important step in the catabolic pathways of valine, isoleucine, threonine, methionine, odd-chain fatty acids, and cholesterol.

The enzyme requires a cofactor called adenosylcobalamin (vitamin B12) for its activity. In the absence of this cofactor or due to mutations in the gene encoding the enzyme, methylmalonyl-CoA mutase deficiency can occur, leading to the accumulation of methylmalonic acid and other toxic metabolites, which can cause a range of symptoms including vomiting, dehydration, lethargy, hypotonia, developmental delay, and metabolic acidosis. This condition is typically inherited in an autosomal recessive manner and can be diagnosed through biochemical tests and genetic analysis.

Medical Definition of Vitamin B6:

Vitamin B6, also known as pyridoxine, is a water-soluble vitamin that plays a crucial role in various bodily functions. It is involved in the process of making serotonin and norepinephrine, which are chemicals that transmit signals in the brain. Vitamin B6 is also necessary for the formation of myelin, a protein layer that forms around nerve cells. Additionally, it helps the body to metabolize proteins, carbohydrates, and fats, and is involved in the creation of red blood cells.

Vitamin B6 can be found in a wide variety of foods, including poultry, seafood, bananas, potatoes, and fortified cereals. A deficiency in vitamin B6 can lead to anemia, confusion, and a weakened immune system. On the other hand, excessive intake of vitamin B6 can cause nerve damage and skin lesions. It is important to maintain appropriate levels of vitamin B6 through a balanced diet and, if necessary, supplementation under the guidance of a healthcare provider.

Biological availability is a term used in pharmacology and toxicology that refers to the degree and rate at which a drug or other substance is absorbed into the bloodstream and becomes available at the site of action in the body. It is a measure of the amount of the substance that reaches the systemic circulation unchanged, after administration by any route (such as oral, intravenous, etc.).

The biological availability (F) of a drug can be calculated using the area under the curve (AUC) of the plasma concentration-time profile after extravascular and intravenous dosing, according to the following formula:

F = (AUCex/AUCiv) x (Doseiv/Doseex)

where AUCex is the AUC after extravascular dosing, AUCiv is the AUC after intravenous dosing, Doseiv is the intravenous dose, and Doseex is the extravascular dose.

Biological availability is an important consideration in drug development and therapy, as it can affect the drug's efficacy, safety, and dosage regimen. Drugs with low biological availability may require higher doses to achieve the desired therapeutic effect, while drugs with high biological availability may have a more rapid onset of action and require lower doses to avoid toxicity.

Biological transport refers to the movement of molecules, ions, or solutes across biological membranes or through cells in living organisms. This process is essential for maintaining homeostasis, regulating cellular functions, and enabling communication between cells. There are two main types of biological transport: passive transport and active transport.

Passive transport does not require the input of energy and includes:

1. Diffusion: The random movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached.
2. Osmosis: The diffusion of solvent molecules (usually water) across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
3. Facilitated diffusion: The assisted passage of polar or charged substances through protein channels or carriers in the cell membrane, which increases the rate of diffusion without consuming energy.

Active transport requires the input of energy (in the form of ATP) and includes:

1. Primary active transport: The direct use of ATP to move molecules against their concentration gradient, often driven by specific transport proteins called pumps.
2. Secondary active transport: The coupling of the movement of one substance down its electrochemical gradient with the uphill transport of another substance, mediated by a shared transport protein. This process is also known as co-transport or counter-transport.

High-performance liquid chromatography (HPLC) is a type of chromatography that separates and analyzes compounds based on their interactions with a stationary phase and a mobile phase under high pressure. The mobile phase, which can be a gas or liquid, carries the sample mixture through a column containing the stationary phase.

In HPLC, the mobile phase is a liquid, and it is pumped through the column at high pressures (up to several hundred atmospheres) to achieve faster separation times and better resolution than other types of liquid chromatography. The stationary phase can be a solid or a liquid supported on a solid, and it interacts differently with each component in the sample mixture, causing them to separate as they travel through the column.

HPLC is widely used in analytical chemistry, pharmaceuticals, biotechnology, and other fields to separate, identify, and quantify compounds present in complex mixtures. It can be used to analyze a wide range of substances, including drugs, hormones, vitamins, pigments, flavors, and pollutants. HPLC is also used in the preparation of pure samples for further study or use.

Neural Tube Defects (NTDs) are a group of birth defects that affect the brain, spine, or spinal cord. They occur when the neural tube, which forms the early brain and spinal cord of the embryo, does not close properly during fetal development. This can result in various conditions such as:

1. Anencephaly: a severe defect where most of the brain and skull are missing. Infants with anencephaly are usually stillborn or die shortly after birth.
2. Spina bifida: a condition where the spine does not close properly, leaving a portion of the spinal cord and nerves exposed. This can result in various neurological problems, including paralysis, bladder and bowel dysfunction, and hydrocephalus (fluid buildup in the brain).
3. Encephalocele: a condition where the skull does not close properly, allowing the brain to protrude through an opening in the skull. This can result in various neurological problems, including developmental delays, vision and hearing impairments, and seizures.

NTDs are thought to be caused by a combination of genetic and environmental factors, such as folic acid deficiency, obesity, diabetes, and exposure to certain medications during pregnancy. Folic acid supplementation before and during early pregnancy has been shown to reduce the risk of NTDs.

Pernicious anemia is a specific type of vitamin B12 deficiency anemia that is caused by a lack of intrinsic factor, a protein made in the stomach that is needed to absorb vitamin B12. The absence of intrinsic factor leads to poor absorption of vitamin B12 from food and results in its deficiency.

Vitamin B12 is essential for the production of healthy red blood cells, which carry oxygen throughout the body. Without enough vitamin B12, the body cannot produce enough red blood cells, leading to anemia. Pernicious anemia typically develops slowly over several years and can cause symptoms such as fatigue, weakness, pale skin, shortness of breath, and a decreased appetite.

Pernicious anemia is an autoimmune disorder, which means that the body's immune system mistakenly attacks healthy cells in the stomach lining, leading to a loss of intrinsic factor production. It is more common in older adults, particularly those over 60 years old, and can also be associated with other autoimmune disorders such as type 1 diabetes, Hashimoto's thyroiditis, and Addison's disease.

Treatment for pernicious anemia typically involves vitamin B12 replacement therapy, either through oral supplements or injections of the vitamin. In some cases, dietary changes may also be recommended to ensure adequate intake of vitamin B12-rich foods such as meat, fish, poultry, and dairy products.

Biopterin is a type of pteridine compound that acts as a cofactor in various biological reactions, particularly in the metabolism of amino acids such as phenylalanine and tyrosine. It plays a crucial role in the production of neurotransmitters like dopamine, serotonin, and noradrenaline. Biopterin exists in two major forms: tetrahydrobiopterin (BH4) and dihydrobiopterin (BH2). BH4 is the active form that participates in enzymatic reactions, while BH2 is an oxidized form that can be reduced back to BH4 by the action of dihydrobiopterin reductase.

Deficiencies in biopterin metabolism have been linked to several neurological disorders, including phenylketonuria (PKU), dopamine-responsive dystonia, and certain forms of autism. In these conditions, the impaired synthesis or recycling of biopterin can lead to reduced levels of neurotransmitters, causing various neurological symptoms.

Cystathionine is a non-proteinogenic amino acid, which means that it is not used in the synthesis of proteins. It is an intermediate in the biosynthetic pathway that converts the amino acid methionine to cysteine in the body. This process involves the removal of a sulfur atom from methionine, resulting in the formation of cystathionine. Further breakdown of cystathionine leads to the production of cysteine and another amino acid called alpha-ketobutyrate.

Cystathionine plays a crucial role in the metabolism of certain sulfur-containing amino acids, and its levels are regulated by an enzyme called cystathionine beta-synthase (CBS). Genetic defects or deficiencies in this enzyme can result in a disorder known as homocystinuria, which is characterized by the accumulation of homocysteine and methionine in the body and an increased risk of various health complications.

In summary, cystathionine is a biologically important amino acid that functions as an intermediate in the conversion of methionine to cysteine, and its levels are tightly regulated by enzymatic processes in the body.

The liver is a large, solid organ located in the upper right portion of the abdomen, beneath the diaphragm and above the stomach. It plays a vital role in several bodily functions, including:

1. Metabolism: The liver helps to metabolize carbohydrates, fats, and proteins from the food we eat into energy and nutrients that our bodies can use.
2. Detoxification: The liver detoxifies harmful substances in the body by breaking them down into less toxic forms or excreting them through bile.
3. Synthesis: The liver synthesizes important proteins, such as albumin and clotting factors, that are necessary for proper bodily function.
4. Storage: The liver stores glucose, vitamins, and minerals that can be released when the body needs them.
5. Bile production: The liver produces bile, a digestive juice that helps to break down fats in the small intestine.
6. Immune function: The liver plays a role in the immune system by filtering out bacteria and other harmful substances from the blood.

Overall, the liver is an essential organ that plays a critical role in maintaining overall health and well-being.

Molecular sequence data refers to the specific arrangement of molecules, most commonly nucleotides in DNA or RNA, or amino acids in proteins, that make up a biological macromolecule. This data is generated through laboratory techniques such as sequencing, and provides information about the exact order of the constituent molecules. This data is crucial in various fields of biology, including genetics, evolution, and molecular biology, allowing for comparisons between different organisms, identification of genetic variations, and studies of gene function and regulation.

Erythrocytes, also known as red blood cells (RBCs), are the most common type of blood cell in circulating blood in mammals. They are responsible for transporting oxygen from the lungs to the body's tissues and carbon dioxide from the tissues to the lungs.

Erythrocytes are formed in the bone marrow and have a biconcave shape, which allows them to fold and bend easily as they pass through narrow blood vessels. They do not have a nucleus or mitochondria, which makes them more flexible but also limits their ability to reproduce or repair themselves.

In humans, erythrocytes are typically disc-shaped and measure about 7 micrometers in diameter. They contain the protein hemoglobin, which binds to oxygen and gives blood its red color. The lifespan of an erythrocyte is approximately 120 days, after which it is broken down in the liver and spleen.

Abnormalities in erythrocyte count or function can lead to various medical conditions, such as anemia, polycythemia, and sickle cell disease.

Phosphatidylethanolamine N-Methyltransferase (PEMT) is an enzyme that plays a role in the synthesis of phosphatidylcholine, a major phospholipid component of cell membranes. The enzyme catalyzes the transfer of methyl groups from S-adenosylmethionine to phosphatidylethanolamine, converting it into phosphatidylcholine in a three-step methylation process. This enzyme is found primarily in the endoplasmic reticulum and mitochondria of cells and has implications in lipid metabolism, liver function, and inflammation. Genetic variations and altered expression levels of PEMT have been associated with various diseases, including non-alcoholic fatty liver disease, cardiovascular disease, and neurological disorders.

Histones are highly alkaline proteins found in the chromatin of eukaryotic cells. They are rich in basic amino acid residues, such as arginine and lysine, which give them their positive charge. Histones play a crucial role in packaging DNA into a more compact structure within the nucleus by forming a complex with it called a nucleosome. Each nucleosome contains about 146 base pairs of DNA wrapped around an octamer of eight histone proteins (two each of H2A, H2B, H3, and H4). The N-terminal tails of these histones are subject to various post-translational modifications, such as methylation, acetylation, and phosphorylation, which can influence chromatin structure and gene expression. Histone variants also exist, which can contribute to the regulation of specific genes and other nuclear processes.

Genotype, in genetics, refers to the complete heritable genetic makeup of an individual organism, including all of its genes. It is the set of instructions contained in an organism's DNA for the development and function of that organism. The genotype is the basis for an individual's inherited traits, and it can be contrasted with an individual's phenotype, which refers to the observable physical or biochemical characteristics of an organism that result from the expression of its genes in combination with environmental influences.

It is important to note that an individual's genotype is not necessarily identical to their genetic sequence. Some genes have multiple forms called alleles, and an individual may inherit different alleles for a given gene from each parent. The combination of alleles that an individual inherits for a particular gene is known as their genotype for that gene.

Understanding an individual's genotype can provide important information about their susceptibility to certain diseases, their response to drugs and other treatments, and their risk of passing on inherited genetic disorders to their offspring.

Protein O-Methyltransferases (also known as Protein OMTs) are a class of enzymes that catalyze the transfer of methyl groups from a donor molecule, such as S-adenosylmethionine (SAM), to the oxygen atom of specific amino acid residues in proteins. This post-translational modification plays a crucial role in various cellular processes, including epigenetic regulation, signal transduction, and protein stability.

The reaction catalyzed by Protein O-Methyltransferases can be represented as follows:

Protein + SAM → Protein (O-methylated) + S-adenosylhomocysteine

These enzymes specifically recognize their target proteins and methylate particular residues, such as lysine, arginine, serine, threonine, or tyrosine. The methylation of these residues can alter protein function, localization, or interaction with other molecules, thereby regulating various cellular pathways. Dysregulation of Protein O-Methyltransferases has been implicated in several diseases, including cancer and neurological disorders.

Guanidinoacetate N-Methyltransferase (GAMT) is an enzyme that plays a crucial role in the biosynthesis of creatine, a nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to all cells in the body, primarily muscle.

The GAMT enzyme catalyzes the reaction of guanidinoacetate and a methyl group donor (S-adenosylmethionine) to produce creatine, as well as S-adenosylhomocysteine. A deficiency in this enzyme leads to a rare genetic disorder called Guanidinoacetate Methyltransferase Deficiency (GAMT deficiency), which is characterized by an accumulation of guanidinoacetate in the body and low levels of creatine, resulting in neurological symptoms such as developmental delay, seizures, and movement disorders.

Phosphatidyl-N-methylethanolamine N-methyltransferase (PE NMT) is an enzyme that plays a role in the synthesis of phosphatidylcholine, a key component of cell membranes. The enzyme catalyzes the methylation of phosphatidyl-N-methylethanolamine to form phosphatidylcholine in a three-step process, involving the addition of three methyl groups donated by S-adenosylmethionine (SAM). This enzyme is found in various tissues, including the liver, brain, and kidneys. Defects in PE NMT have been associated with certain types of neurological disorders.

Homocysteine S-methyltransferase is not a commonly used medical term, but it does refer to an enzyme that is important in the metabolism of the amino acid homocysteine. The proper medical term for this enzyme is actually "5-methyltetrahydrofolate-homocysteine methyltransferase" or simply "methionine synthase."

Methionine synthase plays a crucial role in the conversion of homocysteine to methionine, which is an essential amino acid that cannot be synthesized by the body and must be obtained through diet. The enzyme requires several cofactors, including vitamin B12 (cobalamin) and folate (vitamin B9), to function properly.

Deficiencies in methionine synthase or its cofactors can lead to an accumulation of homocysteine in the blood, a condition known as hyperhomocysteinemia. Elevated levels of homocysteine have been linked to several health problems, including cardiovascular disease, neurological disorders, and birth defects. Therefore, maintaining adequate levels of methionine synthase and its cofactors is essential for overall health and well-being.

Homocystinuria is a genetic disorder characterized by the accumulation of homocysteine and its metabolites in the body due to a deficiency in the enzyme cystathionine beta-synthase (CBS). This enzyme is responsible for converting homocysteine to cystathionine, which is a critical step in the metabolic pathway that breaks down methionine.

As a result of this deficiency, homocysteine levels in the blood increase and can lead to various health problems, including neurological impairment, ocular abnormalities (such as ectopia lentis or dislocation of the lens), skeletal abnormalities (such as Marfan-like features), and vascular complications.

Homocystinuria can be diagnosed through newborn screening or by measuring homocysteine levels in the blood or urine. Treatment typically involves a low-methionine diet, supplementation with vitamin B6 (pyridoxine), betaine, and/or methylcobalamin (a form of vitamin B12) to help reduce homocysteine levels and prevent complications associated with the disorder.

Acetyl Coenzyme A, often abbreviated as Acetyl-CoA, is a key molecule in metabolism, particularly in the breakdown and oxidation of carbohydrates, fats, and proteins to produce energy. It is a coenzyme that plays a central role in the cellular process of transforming the energy stored in the chemical bonds of nutrients into a form that the cell can use.

Acetyl-CoA consists of an acetyl group (two carbon atoms) linked to coenzyme A, a complex organic molecule. This linkage is facilitated by an enzyme called acetyltransferase. Once formed, Acetyl-CoA can enter various metabolic pathways. In the citric acid cycle (also known as the Krebs cycle), Acetyl-CoA is further oxidized to release energy in the form of ATP, NADH, and FADH2, which are used in other cellular processes. Additionally, Acetyl-CoA is involved in the biosynthesis of fatty acids, cholesterol, and certain amino acids.

In summary, Acetyl Coenzyme A is a vital molecule in metabolism that connects various biochemical pathways for energy production and biosynthesis.

An amino acid sequence is the specific order of amino acids in a protein or peptide molecule, formed by the linking of the amino group (-NH2) of one amino acid to the carboxyl group (-COOH) of another amino acid through a peptide bond. The sequence is determined by the genetic code and is unique to each type of protein or peptide. It plays a crucial role in determining the three-dimensional structure and function of proteins.

A mutation is a permanent change in the DNA sequence of an organism's genome. Mutations can occur spontaneously or be caused by environmental factors such as exposure to radiation, chemicals, or viruses. They may have various effects on the organism, ranging from benign to harmful, depending on where they occur and whether they alter the function of essential proteins. In some cases, mutations can increase an individual's susceptibility to certain diseases or disorders, while in others, they may confer a survival advantage. Mutations are the driving force behind evolution, as they introduce new genetic variability into populations, which can then be acted upon by natural selection.

Azacitidine is a medication that is primarily used to treat myelodysplastic syndrome (MDS), a type of cancer where the bone marrow does not produce enough healthy blood cells. It is also used to treat acute myeloid leukemia (AML) in some cases.

Azacitidine is a type of drug known as a hypomethylating agent, which means that it works by modifying the way that genes are expressed in cancer cells. Specifically, azacitidine inhibits the activity of an enzyme called DNA methyltransferase, which adds methyl groups to the DNA molecule and can silence the expression of certain genes. By inhibiting this enzyme, azacitidine can help to restore the normal function of genes that have been silenced in cancer cells.

Azacitidine is typically given as a series of subcutaneous (under the skin) or intravenous (into a vein) injections over a period of several days, followed by a rest period of several weeks before the next cycle of treatment. The specific dosage and schedule may vary depending on the individual patient's needs and response to treatment.

Like all medications, azacitidine can have side effects, which may include nausea, vomiting, diarrhea, constipation, fatigue, fever, and decreased appetite. More serious side effects are possible, but relatively rare, and may include bone marrow suppression, infections, and liver damage. Patients receiving azacitidine should be closely monitored by their healthcare provider to manage any side effects that may occur.

Genetic polymorphism refers to the occurrence of multiple forms (called alleles) of a particular gene within a population. These variations in the DNA sequence do not generally affect the function or survival of the organism, but they can contribute to differences in traits among individuals. Genetic polymorphisms can be caused by single nucleotide changes (SNPs), insertions or deletions of DNA segments, or other types of genetic rearrangements. They are important for understanding genetic diversity and evolution, as well as for identifying genetic factors that may contribute to disease susceptibility in humans.

Glutamates are the salt or ester forms of glutamic acid, which is a naturally occurring amino acid and the most abundant excitatory neurotransmitter in the central nervous system. Glutamate plays a crucial role in various brain functions, such as learning, memory, and cognition. However, excessive levels of glutamate can lead to neuronal damage or death, contributing to several neurological disorders, including stroke, epilepsy, and neurodegenerative diseases like Alzheimer's and Parkinson's.

Glutamates are also commonly found in food as a natural flavor enhancer, often listed under the name monosodium glutamate (MSG). While MSG has been extensively studied, its safety remains a topic of debate, with some individuals reporting adverse reactions after consuming foods containing this additive.

A homozygote is an individual who has inherited the same allele (version of a gene) from both parents and therefore possesses two identical copies of that allele at a specific genetic locus. This can result in either having two dominant alleles (homozygous dominant) or two recessive alleles (homozygous recessive). In contrast, a heterozygote has inherited different alleles from each parent for a particular gene.

The term "homozygote" is used in genetics to describe the genetic makeup of an individual at a specific locus on their chromosomes. Homozygosity can play a significant role in determining an individual's phenotype (observable traits), as having two identical alleles can strengthen the expression of certain characteristics compared to having just one dominant and one recessive allele.

Substrate specificity in the context of medical biochemistry and enzymology refers to the ability of an enzyme to selectively bind and catalyze a chemical reaction with a particular substrate (or a group of similar substrates) while discriminating against other molecules that are not substrates. This specificity arises from the three-dimensional structure of the enzyme, which has evolved to match the shape, charge distribution, and functional groups of its physiological substrate(s).

Substrate specificity is a fundamental property of enzymes that enables them to carry out highly selective chemical transformations in the complex cellular environment. The active site of an enzyme, where the catalysis takes place, has a unique conformation that complements the shape and charge distribution of its substrate(s). This ensures efficient recognition, binding, and conversion of the substrate into the desired product while minimizing unwanted side reactions with other molecules.

Substrate specificity can be categorized as:

1. Absolute specificity: An enzyme that can only act on a single substrate or a very narrow group of structurally related substrates, showing no activity towards any other molecule.
2. Group specificity: An enzyme that prefers to act on a particular functional group or class of compounds but can still accommodate minor structural variations within the substrate.
3. Broad or promiscuous specificity: An enzyme that can act on a wide range of structurally diverse substrates, albeit with varying catalytic efficiencies.

Understanding substrate specificity is crucial for elucidating enzymatic mechanisms, designing drugs that target specific enzymes or pathways, and developing biotechnological applications that rely on the controlled manipulation of enzyme activities.

'Methanosarcina barkeri' is not a medical term, but a species name in the domain of microbiology. It refers to a type of archaea (single-celled organisms) that is capable of methanogenesis - producing methane as a metabolic byproduct. This microorganism is commonly found in anaerobic environments such as wetlands, digestive tracts of animals, and sewage sludge. It's not something that typically has a direct medical definition or relevance, unless in the context of specific research or environmental/industrial settings.

Polycomb Repressive Complex 2 (PRC2) is a multi-protein complex that plays a crucial role in the epigenetic regulation of gene expression, primarily through the modification of histone proteins. It is named after the Polycomb group genes that were initially identified in Drosophila melanogaster (fruit flies) due to their involvement in maintaining the repressed state of homeotic genes during development.

The core components of PRC2 include:

1. Enhancer of Zeste Homolog 2 (EZH2) or its paralog EZH1: These are histone methyltransferases that catalyze the addition of methyl groups to lysine 27 on histone H3 (H3K27). The trimethylation of this residue (H3K27me3) is a hallmark of PRC2-mediated repression.
2. Suppressor of Zeste 12 (SUZ12): This protein is essential for the stability and methyltransferase activity of the complex.
3. Embryonic Ectoderm Development (EED): This protein recognizes and binds to the H3K27me3 mark, enhancing the methyltransferase activity of EZH2/EZH1 and promoting the spreading of the repressive mark along chromatin.
4. Retinoblastoma-associated Protein 46/48 (RbAP46/48): These are histone binding proteins that facilitate the interaction between PRC2 and nucleosomes, thereby contributing to the specificity of its targeting.

PRC2 is involved in various cellular processes, such as differentiation, proliferation, and development, by modulating the expression of genes critical for these functions. Dysregulation of PRC2 has been implicated in several human diseases, including cancers, where it often exhibits aberrant activity or mislocalization, leading to altered gene expression profiles.

Tetrahydrofolate dehydrogenase (EC 1.5.1.20) is an enzyme involved in folate metabolism. The enzyme catalyzes the oxidation of tetrahydrofolate (THF) to dihydrofolate (DHF), while simultaneously reducing NADP+ to NADPH.

The reaction can be summarized as follows:

THF + NADP+ -> DHF + NADPH + H+

This enzyme plays a crucial role in the synthesis of purines and thymidylate, which are essential components of DNA and RNA. Therefore, any defects or deficiencies in tetrahydrofolate dehydrogenase can lead to various medical conditions, including megaloblastic anemia and neural tube defects during fetal development.

A base sequence in the context of molecular biology refers to the specific order of nucleotides in a DNA or RNA molecule. In DNA, these nucleotides are adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, uracil (U) takes the place of thymine. The base sequence contains genetic information that is transcribed into RNA and ultimately translated into proteins. It is the exact order of these bases that determines the genetic code and thus the function of the DNA or RNA molecule.

Membrane transport proteins are specialized biological molecules, specifically integral membrane proteins, that facilitate the movement of various substances across the lipid bilayer of cell membranes. They are responsible for the selective and regulated transport of ions, sugars, amino acids, nucleotides, and other molecules into and out of cells, as well as within different cellular compartments. These proteins can be categorized into two main types: channels and carriers (or pumps). Channels provide a passive transport mechanism, allowing ions or small molecules to move down their electrochemical gradient, while carriers actively transport substances against their concentration gradient, requiring energy usually in the form of ATP. Membrane transport proteins play a crucial role in maintaining cell homeostasis, signaling processes, and many other physiological functions.

Medically, "milk" is not defined. However, it is important to note that human babies are fed with breast milk, which is the secretion from the mammary glands of humans. It is rich in nutrients like proteins, fats, carbohydrates (lactose), vitamins and minerals that are essential for growth and development.

Other mammals also produce milk to feed their young. These include cows, goats, and sheep, among others. Their milk is often consumed by humans as a source of nutrition, especially in dairy products. However, the composition of these milks can vary significantly from human breast milk.

Methylmalonic acid (MMA) is an organic compound that is produced in the human body during the metabolism of certain amino acids, including methionine and threonine. It is a type of fatty acid that is intermediate in the breakdown of these amino acids in the liver and other tissues.

Under normal circumstances, MMA is quickly converted to succinic acid, which is then used in the Krebs cycle to generate energy in the form of ATP. However, when there are deficiencies or mutations in enzymes involved in this metabolic pathway, such as methylmalonyl-CoA mutase, MMA can accumulate in the body and cause methylmalonic acidemia, a rare genetic disorder that affects approximately 1 in every 50,000 to 100,000 individuals worldwide.

Elevated levels of MMA in the blood or urine can be indicative of various metabolic disorders, including methylmalonic acidemia, vitamin B12 deficiency, and renal insufficiency. Therefore, measuring MMA levels is often used as a diagnostic tool to help identify and manage these conditions.

A cell line is a culture of cells that are grown in a laboratory for use in research. These cells are usually taken from a single cell or group of cells, and they are able to divide and grow continuously in the lab. Cell lines can come from many different sources, including animals, plants, and humans. They are often used in scientific research to study cellular processes, disease mechanisms, and to test new drugs or treatments. Some common types of human cell lines include HeLa cells (which come from a cancer patient named Henrietta Lacks), HEK293 cells (which come from embryonic kidney cells), and HUVEC cells (which come from umbilical vein endothelial cells). It is important to note that cell lines are not the same as primary cells, which are cells that are taken directly from a living organism and have not been grown in the lab.

Tritium is not a medical term, but it is a term used in the field of nuclear physics and chemistry. Tritium (symbol: T or 3H) is a radioactive isotope of hydrogen with two neutrons and one proton in its nucleus. It is also known as heavy hydrogen or superheavy hydrogen.

Tritium has a half-life of about 12.3 years, which means that it decays by emitting a low-energy beta particle (an electron) to become helium-3. Due to its radioactive nature and relatively short half-life, tritium is used in various applications, including nuclear weapons, fusion reactors, luminous paints, and medical research.

In the context of medicine, tritium may be used as a radioactive tracer in some scientific studies or medical research, but it is not a term commonly used to describe a medical condition or treatment.

Carbon isotopes are variants of the chemical element carbon that have different numbers of neutrons in their atomic nuclei. The most common and stable isotope of carbon is carbon-12 (^{12}C), which contains six protons and six neutrons. However, carbon can also come in other forms, known as isotopes, which contain different numbers of neutrons.

Carbon-13 (^{13}C) is a stable isotope of carbon that contains seven neutrons in its nucleus. It makes up about 1.1% of all carbon found on Earth and is used in various scientific applications, such as in tracing the metabolic pathways of organisms or in studying the age of fossilized materials.

Carbon-14 (^{14}C), also known as radiocarbon, is a radioactive isotope of carbon that contains eight neutrons in its nucleus. It is produced naturally in the atmosphere through the interaction of cosmic rays with nitrogen gas. Carbon-14 has a half-life of about 5,730 years, which makes it useful for dating organic materials, such as archaeological artifacts or fossils, up to around 60,000 years old.

Carbon isotopes are important in many scientific fields, including geology, biology, and medicine, and are used in a variety of applications, from studying the Earth's climate history to diagnosing medical conditions.

Lysine is an essential amino acid, which means that it cannot be synthesized by the human body and must be obtained through the diet. Its chemical formula is (2S)-2,6-diaminohexanoic acid. Lysine is necessary for the growth and maintenance of tissues in the body, and it plays a crucial role in the production of enzymes, hormones, and antibodies. It is also essential for the absorption of calcium and the formation of collagen, which is an important component of bones and connective tissue. Foods that are good sources of lysine include meat, poultry, fish, eggs, and dairy products.

Epigenetics is the study of heritable changes in gene function that occur without a change in the underlying DNA sequence. These changes can be caused by various mechanisms such as DNA methylation, histone modification, and non-coding RNA molecules. Epigenetic changes can be influenced by various factors including age, environment, lifestyle, and disease state.

Genetic epigenesis specifically refers to the study of how genetic factors influence these epigenetic modifications. Genetic variations between individuals can lead to differences in epigenetic patterns, which in turn can contribute to phenotypic variation and susceptibility to diseases. For example, certain genetic variants may predispose an individual to develop cancer, and environmental factors such as smoking or exposure to chemicals can interact with these genetic variants to trigger epigenetic changes that promote tumor growth.

Overall, the field of genetic epigenesis aims to understand how genetic and environmental factors interact to regulate gene expression and contribute to disease susceptibility.

Cytosine is one of the four nucleobases in the nucleic acid molecules DNA and RNA, along with adenine, guanine, and thymine (in DNA) or uracil (in RNA). The single-letter abbreviation for cytosine is "C."

Cytosine base pairs specifically with guanine through hydrogen bonding, forming a base pair. In DNA, the double helix consists of two complementary strands of nucleotides held together by these base pairs, such that the sequence of one strand determines the sequence of the other. This property is critical for DNA replication and transcription, processes that are essential for life.

Cytosine residues in DNA can undergo spontaneous deamination to form uracil, which can lead to mutations if not corrected by repair mechanisms. In RNA, cytosine can be methylated at the 5-carbon position to form 5-methylcytosine, a modification that plays a role in regulating gene expression and other cellular processes.

Gene silencing is a process by which the expression of a gene is blocked or inhibited, preventing the production of its corresponding protein. This can occur naturally through various mechanisms such as RNA interference (RNAi), where small RNAs bind to and degrade specific mRNAs, or DNA methylation, where methyl groups are added to the DNA molecule, preventing transcription. Gene silencing can also be induced artificially using techniques such as RNAi-based therapies, antisense oligonucleotides, or CRISPR-Cas9 systems, which allow for targeted suppression of gene expression in research and therapeutic applications.

Oxidation-Reduction (redox) reactions are a type of chemical reaction involving a transfer of electrons between two species. The substance that loses electrons in the reaction is oxidized, and the substance that gains electrons is reduced. Oxidation and reduction always occur together in a redox reaction, hence the term "oxidation-reduction."

In biological systems, redox reactions play a crucial role in many cellular processes, including energy production, metabolism, and signaling. The transfer of electrons in these reactions is often facilitated by specialized molecules called electron carriers, such as nicotinamide adenine dinucleotide (NAD+/NADH) and flavin adenine dinucleotide (FAD/FADH2).

The oxidation state of an element in a compound is a measure of the number of electrons that have been gained or lost relative to its neutral state. In redox reactions, the oxidation state of one or more elements changes as they gain or lose electrons. The substance that is oxidized has a higher oxidation state, while the substance that is reduced has a lower oxidation state.

Overall, oxidation-reduction reactions are fundamental to the functioning of living organisms and are involved in many important biological processes.

In the field of medicine, "time factors" refer to the duration of symptoms or time elapsed since the onset of a medical condition, which can have significant implications for diagnosis and treatment. Understanding time factors is crucial in determining the progression of a disease, evaluating the effectiveness of treatments, and making critical decisions regarding patient care.

For example, in stroke management, "time is brain," meaning that rapid intervention within a specific time frame (usually within 4.5 hours) is essential to administering tissue plasminogen activator (tPA), a clot-busting drug that can minimize brain damage and improve patient outcomes. Similarly, in trauma care, the "golden hour" concept emphasizes the importance of providing definitive care within the first 60 minutes after injury to increase survival rates and reduce morbidity.

Time factors also play a role in monitoring the progression of chronic conditions like diabetes or heart disease, where regular follow-ups and assessments help determine appropriate treatment adjustments and prevent complications. In infectious diseases, time factors are crucial for initiating antibiotic therapy and identifying potential outbreaks to control their spread.

Overall, "time factors" encompass the significance of recognizing and acting promptly in various medical scenarios to optimize patient outcomes and provide effective care.

Hydrogen-ion concentration, also known as pH, is a measure of the acidity or basicity of a solution. It is defined as the negative logarithm (to the base 10) of the hydrogen ion activity in a solution. The standard unit of measurement is the pH unit. A pH of 7 is neutral, less than 7 is acidic, and greater than 7 is basic.

In medical terms, hydrogen-ion concentration is important for maintaining homeostasis within the body. For example, in the stomach, a high hydrogen-ion concentration (low pH) is necessary for the digestion of food. However, in other parts of the body such as blood, a high hydrogen-ion concentration can be harmful and lead to acidosis. Conversely, a low hydrogen-ion concentration (high pH) in the blood can lead to alkalosis. Both acidosis and alkalosis can have serious consequences on various organ systems if not corrected.

Gel chromatography is a type of liquid chromatography that separates molecules based on their size or molecular weight. It uses a stationary phase that consists of a gel matrix made up of cross-linked polymers, such as dextran, agarose, or polyacrylamide. The gel matrix contains pores of various sizes, which allow smaller molecules to penetrate deeper into the matrix while larger molecules are excluded.

In gel chromatography, a mixture of molecules is loaded onto the top of the gel column and eluted with a solvent that moves down the column by gravity or pressure. As the sample components move down the column, they interact with the gel matrix and get separated based on their size. Smaller molecules can enter the pores of the gel and take longer to elute, while larger molecules are excluded from the pores and elute more quickly.

Gel chromatography is commonly used to separate and purify proteins, nucleic acids, and other biomolecules based on their size and molecular weight. It is also used in the analysis of polymers, colloids, and other materials with a wide range of applications in chemistry, biology, and medicine.

"Cells, cultured" is a medical term that refers to cells that have been removed from an organism and grown in controlled laboratory conditions outside of the body. This process is called cell culture and it allows scientists to study cells in a more controlled and accessible environment than they would have inside the body. Cultured cells can be derived from a variety of sources, including tissues, organs, or fluids from humans, animals, or cell lines that have been previously established in the laboratory.

Cell culture involves several steps, including isolation of the cells from the tissue, purification and characterization of the cells, and maintenance of the cells in appropriate growth conditions. The cells are typically grown in specialized media that contain nutrients, growth factors, and other components necessary for their survival and proliferation. Cultured cells can be used for a variety of purposes, including basic research, drug development and testing, and production of biological products such as vaccines and gene therapies.

It is important to note that cultured cells may behave differently than they do in the body, and results obtained from cell culture studies may not always translate directly to human physiology or disease. Therefore, it is essential to validate findings from cell culture experiments using additional models and ultimately in clinical trials involving human subjects.

'Escherichia coli' (E. coli) is a type of gram-negative, facultatively anaerobic, rod-shaped bacterium that commonly inhabits the intestinal tract of humans and warm-blooded animals. It is a member of the family Enterobacteriaceae and one of the most well-studied prokaryotic model organisms in molecular biology.

While most E. coli strains are harmless and even beneficial to their hosts, some serotypes can cause various forms of gastrointestinal and extraintestinal illnesses in humans and animals. These pathogenic strains possess virulence factors that enable them to colonize and damage host tissues, leading to diseases such as diarrhea, urinary tract infections, pneumonia, and sepsis.

E. coli is a versatile organism with remarkable genetic diversity, which allows it to adapt to various environmental niches. It can be found in water, soil, food, and various man-made environments, making it an essential indicator of fecal contamination and a common cause of foodborne illnesses. The study of E. coli has contributed significantly to our understanding of fundamental biological processes, including DNA replication, gene regulation, and protein synthesis.

Cysteine is a semi-essential amino acid, which means that it can be produced by the human body under normal circumstances, but may need to be obtained from external sources in certain conditions such as illness or stress. Its chemical formula is HO2CCH(NH2)CH2SH, and it contains a sulfhydryl group (-SH), which allows it to act as a powerful antioxidant and participate in various cellular processes.

Cysteine plays important roles in protein structure and function, detoxification, and the synthesis of other molecules such as glutathione, taurine, and coenzyme A. It is also involved in wound healing, immune response, and the maintenance of healthy skin, hair, and nails.

Cysteine can be found in a variety of foods, including meat, poultry, fish, dairy products, eggs, legumes, nuts, seeds, and some grains. It is also available as a dietary supplement and can be used in the treatment of various medical conditions such as liver disease, bronchitis, and heavy metal toxicity. However, excessive intake of cysteine may have adverse effects on health, including gastrointestinal disturbances, nausea, vomiting, and headaches.

Stereoisomerism is a type of isomerism (structural arrangement of atoms) in which molecules have the same molecular formula and sequence of bonded atoms, but differ in the three-dimensional orientation of their atoms in space. This occurs when the molecule contains asymmetric carbon atoms or other rigid structures that prevent free rotation, leading to distinct spatial arrangements of groups of atoms around a central point. Stereoisomers can have different chemical and physical properties, such as optical activity, boiling points, and reactivities, due to differences in their shape and the way they interact with other molecules.

There are two main types of stereoisomerism: enantiomers (mirror-image isomers) and diastereomers (non-mirror-image isomers). Enantiomers are pairs of stereoisomers that are mirror images of each other, but cannot be superimposed on one another. Diastereomers, on the other hand, are non-mirror-image stereoisomers that have different physical and chemical properties.

Stereoisomerism is an important concept in chemistry and biology, as it can affect the biological activity of molecules, such as drugs and natural products. For example, some enantiomers of a drug may be active, while others are inactive or even toxic. Therefore, understanding stereoisomerism is crucial for designing and synthesizing effective and safe drugs.

The double-blind method is a study design commonly used in research, including clinical trials, to minimize bias and ensure the objectivity of results. In this approach, both the participants and the researchers are unaware of which group the participants are assigned to, whether it be the experimental group or the control group. This means that neither the participants nor the researchers know who is receiving a particular treatment or placebo, thus reducing the potential for bias in the evaluation of outcomes. The assignment of participants to groups is typically done by a third party not involved in the study, and the codes are only revealed after all data have been collected and analyzed.

Tandem mass spectrometry (MS/MS) is a technique used to identify and quantify specific molecules, such as proteins or metabolites, within complex mixtures. This method uses two or more sequential mass analyzers to first separate ions based on their mass-to-charge ratio and then further fragment the selected ions into smaller pieces for additional analysis. The fragmentation patterns generated in MS/MS experiments can be used to determine the structure and identity of the original molecule, making it a powerful tool in various fields such as proteomics, metabolomics, and forensic science.

Promoter regions in genetics refer to specific DNA sequences located near the transcription start site of a gene. They serve as binding sites for RNA polymerase and various transcription factors that regulate the initiation of gene transcription. These regulatory elements help control the rate of transcription and, therefore, the level of gene expression. Promoter regions can be composed of different types of sequences, such as the TATA box and CAAT box, and their organization and composition can vary between different genes and species.

Adenosylhomocysteinase is an enzyme that plays a crucial role in the methionine cycle, which is a biochemical pathway involved in the synthesis and metabolism of various essential molecules in the body. The formal medical definition of adenosylhomocysteinase is:

"An enzyme that catalyzes the reversible conversion of S-adenosylhomocysteine to homocysteine and adenosine. This reaction is the first step in the recycling of methionine, a sulfur-containing amino acid that is essential for various metabolic processes, including the synthesis of proteins, neurotransmitters, and phospholipids."

In simpler terms, adenosylhomocysteinase helps break down S-adenosylhomocysteine, a byproduct of methylation reactions in the body, into its component parts: homocysteine and adenosine. This breakdown is essential for the proper functioning of the methionine cycle and the maintenance of normal levels of homocysteine, which can be toxic at high concentrations.

Deficiencies or mutations in the adenosylhomocysteinase gene can lead to an accumulation of S-adenosylhomocysteine and homocysteine, which can contribute to various health issues, including neurological disorders, cardiovascular disease, and developmental abnormalities.

Pyridoxine is the chemical name for Vitamin B6. According to the medical definition, Pyridoxine is a water-soluble vitamin that is part of the B-vitamin complex and is essential for the metabolism of proteins, carbohydrates, and fats. It plays a vital role in the regulation of homocysteine levels in the body, the formation of neurotransmitters such as serotonin and dopamine, and the synthesis of hemoglobin.

Pyridoxine can be found naturally in various foods, including whole grains, legumes, vegetables, nuts, seeds, meat, poultry, and fish. It is also available as a dietary supplement and may be prescribed by healthcare providers to treat or prevent certain medical conditions, such as vitamin B6 deficiency, anemia, seizures, and carpal tunnel syndrome.

Like other water-soluble vitamins, Pyridoxine cannot be stored in the body and must be replenished regularly through diet or supplementation. Excessive intake of Pyridoxine can lead to toxicity symptoms such as nerve damage, skin lesions, and light sensitivity.

A kidney, in medical terms, is one of two bean-shaped organs located in the lower back region of the body. They are essential for maintaining homeostasis within the body by performing several crucial functions such as:

1. Regulation of water and electrolyte balance: Kidneys help regulate the amount of water and various electrolytes like sodium, potassium, and calcium in the bloodstream to maintain a stable internal environment.

2. Excretion of waste products: They filter waste products from the blood, including urea (a byproduct of protein metabolism), creatinine (a breakdown product of muscle tissue), and other harmful substances that result from normal cellular functions or external sources like medications and toxins.

3. Endocrine function: Kidneys produce several hormones with important roles in the body, such as erythropoietin (stimulates red blood cell production), renin (regulates blood pressure), and calcitriol (activated form of vitamin D that helps regulate calcium homeostasis).

4. pH balance regulation: Kidneys maintain the proper acid-base balance in the body by excreting either hydrogen ions or bicarbonate ions, depending on whether the blood is too acidic or too alkaline.

5. Blood pressure control: The kidneys play a significant role in regulating blood pressure through the renin-angiotensin-aldosterone system (RAAS), which constricts blood vessels and promotes sodium and water retention to increase blood volume and, consequently, blood pressure.

Anatomically, each kidney is approximately 10-12 cm long, 5-7 cm wide, and 3 cm thick, with a weight of about 120-170 grams. They are surrounded by a protective layer of fat and connected to the urinary system through the renal pelvis, ureters, bladder, and urethra.

CpG islands are defined as short stretches of DNA that are characterized by a higher than expected frequency of CpG dinucleotides. A dinucleotide is a pair of adjacent nucleotides, and in the case of CpG, C represents cytosine and G represents guanine. These islands are typically found in the promoter regions of genes, where they play important roles in regulating gene expression.

Under normal circumstances, the cytosine residue in a CpG dinucleotide is often methylated, meaning that a methyl group (-CH3) is added to the cytosine base. However, in CpG islands, methylation is usually avoided, and these regions tend to be unmethylated. This has important implications for gene expression because methylation of CpG dinucleotides in promoter regions can lead to the silencing of genes.

CpG islands are also often targets for transcription factors, which bind to specific DNA sequences and help regulate gene expression. The unmethylated state of CpG islands is thought to be important for maintaining the accessibility of these regions to transcription factors and other regulatory proteins.

Abnormal methylation patterns in CpG islands have been associated with various diseases, including cancer. In many cancers, CpG islands become aberrantly methylated, leading to the silencing of tumor suppressor genes and contributing to the development and progression of the disease.

Superoxides are partially reduced derivatives of oxygen that contain one extra electron, giving them an overall charge of -1. They are highly reactive and unstable, with the most common superoxide being the hydroxyl radical (•OH-) and the superoxide anion (O2-). Superoxides are produced naturally in the body during metabolic processes, particularly within the mitochondria during cellular respiration. They play a role in various physiological processes, but when produced in excess or not properly neutralized, they can contribute to oxidative stress and damage to cells and tissues, potentially leading to the development of various diseases such as cancer, atherosclerosis, and neurodegenerative disorders.

Protein binding, in the context of medical and biological sciences, refers to the interaction between a protein and another molecule (known as the ligand) that results in a stable complex. This process is often reversible and can be influenced by various factors such as pH, temperature, and concentration of the involved molecules.

In clinical chemistry, protein binding is particularly important when it comes to drugs, as many of them bind to proteins (especially albumin) in the bloodstream. The degree of protein binding can affect a drug's distribution, metabolism, and excretion, which in turn influence its therapeutic effectiveness and potential side effects.

Protein-bound drugs may be less available for interaction with their target tissues, as only the unbound or "free" fraction of the drug is active. Therefore, understanding protein binding can help optimize dosing regimens and minimize adverse reactions.

Temperature, in a medical context, is a measure of the degree of hotness or coldness of a body or environment. It is usually measured using a thermometer and reported in degrees Celsius (°C), degrees Fahrenheit (°F), or kelvin (K). In the human body, normal core temperature ranges from about 36.5-37.5°C (97.7-99.5°F) when measured rectally, and can vary slightly depending on factors such as time of day, physical activity, and menstrual cycle. Elevated body temperature is a common sign of infection or inflammation, while abnormally low body temperature can indicate hypothermia or other medical conditions.

RNA caps are structures found at the 5' end of RNA molecules, including messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). These caps consist of a modified guanine nucleotide (called 7-methylguanosine) that is linked to the first nucleotide of the RNA chain through a triphosphate bridge. The RNA cap plays several important roles in regulating RNA metabolism, including protecting the RNA from degradation by exonucleases, promoting the recognition and binding of the RNA by ribosomes during translation, and modulating the stability and transport of the RNA within the cell.

Sequence homology, amino acid, refers to the similarity in the order of amino acids in a protein or a portion of a protein between two or more species. This similarity can be used to infer evolutionary relationships and functional similarities between proteins. The higher the degree of sequence homology, the more likely it is that the proteins are related and have similar functions. Sequence homology can be determined through various methods such as pairwise alignment or multiple sequence alignment, which compare the sequences and calculate a score based on the number and type of matching amino acids.

I'm sorry for any confusion, but there is no established medical or scientific definition for "Vitamin U." The term was used in the past to refer to a substance found in cabbage juice that seemed to help ulcers, but it's not recognized as a vitamin by modern nutrition standards. It's often referred to as methylmethionine or S-methylmethionine, which is a compound derived from the amino acid methionine. Please consult with a healthcare professional for medical advice.

Sarcosine is not a medical condition or disease, but rather it is an organic compound that is classified as a natural amino acid. It is a metabolite that can be found in the human body, and it is involved in various biochemical processes. Specifically, sarcosine is formed from the conversion of the amino acid glycine by the enzyme glycine sarcosine N-methyltransferase (GSMT) and is then converted to glycine betaine (also known as trimethylglycine) by the enzyme betaine-homocysteine S-methyltransferase (BHMT).

Abnormal levels of sarcosine have been found in various disease states, including cancer. Some studies have suggested that high levels of sarcosine in urine or prostate tissue may be associated with an increased risk of developing prostate cancer or a more aggressive form of the disease. However, more research is needed to confirm these findings and establish the clinical significance of sarcosine as a biomarker for cancer or other diseases.

Tertiary protein structure refers to the three-dimensional arrangement of all the elements (polypeptide chains) of a single protein molecule. It is the highest level of structural organization and results from interactions between various side chains (R groups) of the amino acids that make up the protein. These interactions, which include hydrogen bonds, ionic bonds, van der Waals forces, and disulfide bridges, give the protein its unique shape and stability, which in turn determines its function. The tertiary structure of a protein can be stabilized by various factors such as temperature, pH, and the presence of certain ions. Any changes in these factors can lead to denaturation, where the protein loses its tertiary structure and thus its function.

Medical Definition:

"Risk factors" are any attribute, characteristic or exposure of an individual that increases the likelihood of developing a disease or injury. They can be divided into modifiable and non-modifiable risk factors. Modifiable risk factors are those that can be changed through lifestyle choices or medical treatment, while non-modifiable risk factors are inherent traits such as age, gender, or genetic predisposition. Examples of modifiable risk factors include smoking, alcohol consumption, physical inactivity, and unhealthy diet, while non-modifiable risk factors include age, sex, and family history. It is important to note that having a risk factor does not guarantee that a person will develop the disease, but rather indicates an increased susceptibility.

Repressor proteins are a type of regulatory protein in molecular biology that suppress the transcription of specific genes into messenger RNA (mRNA) by binding to DNA. They function as part of gene regulation processes, often working in conjunction with an operator region and a promoter region within the DNA molecule. Repressor proteins can be activated or deactivated by various signals, allowing for precise control over gene expression in response to changing cellular conditions.

There are two main types of repressor proteins:

1. DNA-binding repressors: These directly bind to specific DNA sequences (operator regions) near the target gene and prevent RNA polymerase from transcribing the gene into mRNA.
2. Allosteric repressors: These bind to effector molecules, which then cause a conformational change in the repressor protein, enabling it to bind to DNA and inhibit transcription.

Repressor proteins play crucial roles in various biological processes, such as development, metabolism, and stress response, by controlling gene expression patterns in cells.

Dacarbazine is a medical term that refers to a chemotherapeutic agent used in the treatment of various types of cancer. It is an alkylating agent, which means it works by modifying the DNA of cancer cells, preventing them from dividing and growing. Dacarbazine is often used to treat malignant melanoma, Hodgkin's lymphoma, and soft tissue sarcomas.

The drug is typically administered intravenously in a hospital or clinic setting, and the dosage and schedule may vary depending on the type and stage of cancer being treated, as well as the patient's overall health and response to treatment. Common side effects of dacarbazine include nausea, vomiting, loss of appetite, and weakness or fatigue. More serious side effects, such as low white blood cell counts, anemia, and liver damage, may also occur.

It is important for patients receiving dacarbazine to follow their doctor's instructions carefully and report any unusual symptoms or side effects promptly. Regular monitoring of blood counts and other laboratory tests may be necessary to ensure safe and effective treatment.

Antineoplastic agents, alkylating, are a class of chemotherapeutic drugs that work by alkylating (adding alkyl groups) to DNA, which can lead to the death or dysfunction of cancer cells. These agents can form cross-links between strands of DNA, preventing DNA replication and transcription, ultimately leading to cell cycle arrest and apoptosis (programmed cell death). Examples of alkylating agents include cyclophosphamide, melphalan, and cisplatin. While these drugs are designed to target rapidly dividing cancer cells, they can also affect normal cells that divide quickly, such as those in the bone marrow and digestive tract, leading to side effects like anemia, neutropenia, thrombocytopenia, and nausea/vomiting.

The Myeloid-Lymphoid Leukemia (MLL) protein, also known as MLL1 or HRX, is a histone methyltransferase that plays a crucial role in the regulation of gene expression. It is involved in various cellular processes, including embryonic development and hematopoiesis (the formation of blood cells).

The MLL protein is encoded by the MLL gene, which is located on chromosome 11q23. This gene is frequently rearranged or mutated in certain types of leukemia, leading to the production of abnormal fusion proteins that contribute to tumor development and progression. These MLL-rearranged leukemias are aggressive and have a poor prognosis, making them an important area of research in the field of oncology.

Guanine is not a medical term per se, but it is a biological molecule that plays a crucial role in the body. Guanine is one of the four nucleobases found in the nucleic acids DNA and RNA, along with adenine, cytosine, and thymine (in DNA) or uracil (in RNA). Specifically, guanine pairs with cytosine via hydrogen bonds to form a base pair.

Guanine is a purine derivative, which means it has a double-ring structure. It is formed through the synthesis of simpler molecules in the body and is an essential component of genetic material. Guanine's chemical formula is C5H5N5O.

While guanine itself is not a medical term, abnormalities or mutations in genes that contain guanine nucleotides can lead to various medical conditions, including genetic disorders and cancer.

Genetic transcription is the process by which the information in a strand of DNA is used to create a complementary RNA molecule. This process is the first step in gene expression, where the genetic code in DNA is converted into a form that can be used to produce proteins or functional RNAs.

During transcription, an enzyme called RNA polymerase binds to the DNA template strand and reads the sequence of nucleotide bases. As it moves along the template, it adds complementary RNA nucleotides to the growing RNA chain, creating a single-stranded RNA molecule that is complementary to the DNA template strand. Once transcription is complete, the RNA molecule may undergo further processing before it can be translated into protein or perform its functional role in the cell.

Transcription can be either "constitutive" or "regulated." Constitutive transcription occurs at a relatively constant rate and produces essential proteins that are required for basic cellular functions. Regulated transcription, on the other hand, is subject to control by various intracellular and extracellular signals, allowing cells to respond to changing environmental conditions or developmental cues.

Molecular cloning is a laboratory technique used to create multiple copies of a specific DNA sequence. This process involves several steps:

1. Isolation: The first step in molecular cloning is to isolate the DNA sequence of interest from the rest of the genomic DNA. This can be done using various methods such as PCR (polymerase chain reaction), restriction enzymes, or hybridization.
2. Vector construction: Once the DNA sequence of interest has been isolated, it must be inserted into a vector, which is a small circular DNA molecule that can replicate independently in a host cell. Common vectors used in molecular cloning include plasmids and phages.
3. Transformation: The constructed vector is then introduced into a host cell, usually a bacterial or yeast cell, through a process called transformation. This can be done using various methods such as electroporation or chemical transformation.
4. Selection: After transformation, the host cells are grown in selective media that allow only those cells containing the vector to grow. This ensures that the DNA sequence of interest has been successfully cloned into the vector.
5. Amplification: Once the host cells have been selected, they can be grown in large quantities to amplify the number of copies of the cloned DNA sequence.

Molecular cloning is a powerful tool in molecular biology and has numerous applications, including the production of recombinant proteins, gene therapy, functional analysis of genes, and genetic engineering.

Deoxyribonucleic acid (DNA) is the genetic material present in the cells of organisms where it is responsible for the storage and transmission of hereditary information. DNA is a long molecule that consists of two strands coiled together to form a double helix. Each strand is made up of a series of four nucleotide bases - adenine (A), guanine (G), cytosine (C), and thymine (T) - that are linked together by phosphate and sugar groups. The sequence of these bases along the length of the molecule encodes genetic information, with A always pairing with T and C always pairing with G. This base-pairing allows for the replication and transcription of DNA, which are essential processes in the functioning and reproduction of all living organisms.

In the context of medical and biological sciences, a "binding site" refers to a specific location on a protein, molecule, or cell where another molecule can attach or bind. This binding interaction can lead to various functional changes in the original protein or molecule. The other molecule that binds to the binding site is often referred to as a ligand, which can be a small molecule, ion, or even another protein.

The binding between a ligand and its target binding site can be specific and selective, meaning that only certain ligands can bind to particular binding sites with high affinity. This specificity plays a crucial role in various biological processes, such as signal transduction, enzyme catalysis, or drug action.

In the case of drug development, understanding the location and properties of binding sites on target proteins is essential for designing drugs that can selectively bind to these sites and modulate protein function. This knowledge can help create more effective and safer therapeutic options for various diseases.

Vitamin B deficiency refers to a condition where an individual's body lacks adequate amounts of one or more essential Vitamin B compounds, including Vitamin B1 (thiamin), Vitamin B2 (riboflavin), Vitamin B3 (niacin), Vitamin B5 (pantothenic acid), Vitamin B6 (pyridoxine), Vitamin B7 (biotin), Vitamin B9 (folate), and Vitamin B12 (cobalamin). These water-soluble vitamins play crucial roles in various bodily functions, such as energy production, nerve function, DNA repair, and the formation of red blood cells.

Deficiency in any of these Vitamin B compounds can lead to specific health issues. For instance:

1. Vitamin B1 (thiamin) deficiency can cause beriberi, a condition characterized by muscle weakness, peripheral neuropathy, and heart failure.
2. Vitamin B2 (riboflavin) deficiency may result in ariboflavinosis, which presents with inflammation of the mouth and tongue, anemia, and skin disorders.
3. Vitamin B3 (niacin) deficiency can lead to pellagra, marked by diarrhea, dermatitis, dementia, and, if left untreated, death.
4. Vitamin B5 (pantothenic acid) deficiency is rare but can cause acne-like skin lesions and neurological symptoms.
5. Vitamin B6 (pyridoxine) deficiency may result in anemia, peripheral neuropathy, seizures, and skin disorders.
6. Vitamin B7 (biotin) deficiency can cause hair loss, skin rashes, and neurological symptoms.
7. Vitamin B9 (folate) deficiency can lead to megaloblastic anemia, neural tube defects in fetuses during pregnancy, and increased homocysteine levels, which may contribute to cardiovascular disease.
8. Vitamin B12 (cobalamin) deficiency can cause pernicious anemia, characterized by fatigue, weakness, neurological symptoms, and, if left untreated, irreversible nerve damage.

Deficiencies in these vitamins can arise from inadequate dietary intake, malabsorption syndromes, or certain medications that interfere with absorption or metabolism. It is essential to maintain a balanced diet and consider supplementation if necessary under the guidance of a healthcare professional.

Transcobalamins are a group of proteins in the human body that are responsible for the transport of vitamin B12, also known as cobalamin. There are three main types of transcobalamins:

1. Transcobalamin I (also known as haptocorrin or R-binders): This is a protein produced in various tissues, including the salivary glands and gastric mucosa. It binds to vitamin B12 in the stomach and protects it from degradation by digestive enzymes. However, this form of vitamin B12 is not available for absorption and must be converted to other forms.

2. Transcobalamin II: This is a protein produced mainly in the kidneys and intestines. It binds to vitamin B12 that has been freed from its binding proteins in the stomach and facilitates its absorption in the intestine. Once absorbed, transcobalamin II transports vitamin B12 to tissues throughout the body.

3. Transcobalamin III (also known as intrinsic factor): This is a protein produced by the parietal cells of the stomach. It binds to vitamin B12 and protects it from degradation in the acidic environment of the stomach. Intrinsic factor is essential for the absorption of vitamin B12 in the intestine, as it facilitates its transport across the intestinal wall.

Deficiencies in transcobalamins can lead to vitamin B12 deficiency, which can result in a range of health problems, including anemia, fatigue, neurological symptoms, and developmental delays in children.

Gene expression regulation, enzymologic refers to the biochemical processes and mechanisms that control the transcription and translation of specific genes into functional proteins or enzymes. This regulation is achieved through various enzymatic activities that can either activate or repress gene expression at different levels, such as chromatin remodeling, transcription factor activation, mRNA processing, and protein degradation.

Enzymologic regulation of gene expression involves the action of specific enzymes that catalyze chemical reactions involved in these processes. For example, histone-modifying enzymes can alter the structure of chromatin to make genes more or less accessible for transcription, while RNA polymerase and its associated factors are responsible for transcribing DNA into mRNA. Additionally, various enzymes are involved in post-transcriptional modifications of mRNA, such as splicing, capping, and tailing, which can affect the stability and translation of the transcript.

Overall, the enzymologic regulation of gene expression is a complex and dynamic process that allows cells to respond to changes in their environment and maintain proper physiological function.

In genetics, sequence alignment is the process of arranging two or more DNA, RNA, or protein sequences to identify regions of similarity or homology between them. This is often done using computational methods to compare the nucleotide or amino acid sequences and identify matching patterns, which can provide insight into evolutionary relationships, functional domains, or potential genetic disorders. The alignment process typically involves adjusting gaps and mismatches in the sequences to maximize the similarity between them, resulting in an aligned sequence that can be visually represented and analyzed.

Molecular models are three-dimensional representations of molecular structures that are used in the field of molecular biology and chemistry to visualize and understand the spatial arrangement of atoms and bonds within a molecule. These models can be physical or computer-generated and allow researchers to study the shape, size, and behavior of molecules, which is crucial for understanding their function and interactions with other molecules.

Physical molecular models are often made up of balls (representing atoms) connected by rods or sticks (representing bonds). These models can be constructed manually using materials such as plastic or wooden balls and rods, or they can be created using 3D printing technology.

Computer-generated molecular models, on the other hand, are created using specialized software that allows researchers to visualize and manipulate molecular structures in three dimensions. These models can be used to simulate molecular interactions, predict molecular behavior, and design new drugs or chemicals with specific properties. Overall, molecular models play a critical role in advancing our understanding of molecular structures and their functions.

Isoaspartic acid is not typically considered a medical term, but it does have relevance to the field of medicine and biochemistry. Isoaspartic acid is a type of amino acid that can be formed as a result of a post-translational modification in proteins. Specifically, it's an isomer of aspartic acid where the peptide bond has shifted from its original position, resulting in a more reactive and unstable molecule.

In medicine, the formation of isoaspartic acid can contribute to protein misfolding and aggregation, which have been implicated in various diseases such as Alzheimer's disease, Parkinson's disease, and other neurodegenerative disorders. The accumulation of damaged proteins with isoaspartic acid residues may impair cellular function and lead to tissue damage.

However, it's important to note that the presence of isoaspartic acid alone does not necessarily indicate a medical condition or disease. It can be found in various proteins under normal physiological conditions as well.

Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, which remains unchanged at the end of the reaction. A catalyst lowers the activation energy required for the reaction to occur, thereby allowing the reaction to proceed more quickly and efficiently. This can be particularly important in biological systems, where enzymes act as catalysts to speed up metabolic reactions that are essential for life.

Messenger RNA (mRNA) is a type of RNA (ribonucleic acid) that carries genetic information copied from DNA in the form of a series of three-base code "words," each of which specifies a particular amino acid. This information is used by the cell's machinery to construct proteins, a process known as translation. After being transcribed from DNA, mRNA travels out of the nucleus to the ribosomes in the cytoplasm where protein synthesis occurs. Once the protein has been synthesized, the mRNA may be degraded and recycled. Post-transcriptional modifications can also occur to mRNA, such as alternative splicing and addition of a 5' cap and a poly(A) tail, which can affect its stability, localization, and translation efficiency.

Chromatin is the complex of DNA, RNA, and proteins that make up the chromosomes in the nucleus of a cell. It is responsible for packaging the long DNA molecules into a more compact form that fits within the nucleus. Chromatin is made up of repeating units called nucleosomes, which consist of a histone protein octamer wrapped tightly by DNA. The structure of chromatin can be altered through chemical modifications to the histone proteins and DNA, which can influence gene expression and other cellular processes.

Vitamin B6 deficiency refers to the condition in which there is an insufficient amount of vitamin B6 (pyridoxine) in the body. Vitamin B6 is an essential nutrient that plays a crucial role in various bodily functions, including protein metabolism, neurotransmitter synthesis, hemoglobin production, and immune function.

A deficiency in vitamin B6 can lead to several health issues, such as:

1. Anemia: Vitamin B6 is essential for the production of hemoglobin, a protein in red blood cells that carries oxygen throughout the body. A deficiency in this nutrient can lead to anemia, characterized by fatigue, weakness, and shortness of breath.
2. Peripheral neuropathy: Vitamin B6 deficiency can cause nerve damage, leading to symptoms such as numbness, tingling, and pain in the hands and feet.
3. Depression and cognitive impairment: Pyridoxine is necessary for the synthesis of neurotransmitters like serotonin and dopamine, which are involved in mood regulation. A deficiency in vitamin B6 can lead to depression, irritability, and cognitive decline.
4. Seizures: In severe cases, vitamin B6 deficiency can cause seizures due to the impaired synthesis of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter that helps regulate brain activity.
5. Skin changes: A deficiency in this nutrient can also lead to skin changes, such as dryness, scaling, and cracks around the mouth.

Vitamin B6 deficiency is relatively uncommon in developed countries but can occur in individuals with certain medical conditions, such as malabsorption syndromes, alcoholism, kidney disease, or those taking medications that interfere with vitamin B6 metabolism. Additionally, older adults, pregnant women, and breastfeeding mothers may have an increased need for this nutrient, making them more susceptible to deficiency.

Methyl chloride, also known as methyl chloride or chloromethane, is not typically considered a medical term. However, it is a chemical compound with the formula CH3Cl. It is a colorless and extremely volatile liquid that easily evaporates at room temperature.

In terms of potential health impacts, methyl chloride can be harmful if inhaled, swallowed, or comes into contact with the skin. Exposure to high levels can cause symptoms such as headache, dizziness, irritation of the eyes, nose, and throat, nausea, vomiting, and difficulty breathing. Prolonged exposure or significant inhalation can lead to more severe health effects, including damage to the nervous system, liver, and kidneys.

It is essential to handle methyl chloride with care, following appropriate safety measures and guidelines, to minimize potential health risks.

Tubercidin is not a medical term itself, but it is a type of antibiotic that belongs to the class of compounds known as nucleoside antibiotics. Specifically, tubercidin is a naturally occurring adenine analogue that is produced by several species of Streptomyces bacteria.

Tubercidin has been found to have antimicrobial and antitumor activities. It works by inhibiting the enzyme adenosine deaminase, which plays a crucial role in the metabolism of nucleotides in cells. By inhibiting this enzyme, tubercidin can interfere with DNA and RNA synthesis, leading to cell death.

While tubercidin has shown promise as an anticancer agent in preclinical studies, its clinical use is limited due to its toxicity and potential for causing mutations in normal cells. Therefore, it is primarily used for research purposes to study the mechanisms of nucleotide metabolism and the effects of nucleoside analogues on cell growth and differentiation.

5-Methylcytosine (5mC) is a chemical modification of the nucleotide base cytosine in DNA, where a methyl group (-CH3) is added to the 5th carbon atom of the cytosine ring. This modification is catalyzed by DNA methyltransferase enzymes and plays an essential role in epigenetic regulation of gene expression, genomic imprinting, X-chromosome inactivation, and suppression of transposable elements in eukaryotic cells. Abnormal DNA methylation patterns have been associated with various diseases, including cancer.

Methyltransferase Arakawa's syndrome II Betaine-homocysteine S-methyltransferase GRCh38: Ensembl release 89: ENSG00000116984 - ... "Methionine synthase exists in two distinct conformations that differ in reactivity toward methyltetrahydrofolate, ... The cob-independent MetE consists of two TIM-barrel domains that bind homocysteine and N5-MeTHF individually. The two domains ... March 2003). "Homocysteine remethylation enzyme polymorphisms and increased risks for neural tube defects". Molecular Genetics ...
Chronic homocysteine elevation increases s-adenosyl-L-homocysteine levels, consequently inhibiting methyltransferase activity ... Prenatal diagnosis of this condition is possible using [14C] methyltetrahydrofolate. Mutation analysis in native chorionic ... Homocysteine, a sulfur based amino acid is the main product of methionine demethylation. Elevated homocysteine is an ... A major product of methionine demethylation is homocysteine. Remethylation of homocysteine occurs via a cobalamin dependent ...
SAM is converted to S-Adenosyl homocysteine (SAH) during this process. The breaking of the SAM-methyl bond and the formation of ... Methanol, methyl tetrahydrofolate, mono-, di-, and trimethylamine, methanethiol, methyltetrahydromethanopterin, and ... These types include protein methyltransferases, DNA/RNA methyltransferases, natural product methyltransferases, and non-SAM ... Examples include: Catechol-O-methyltransferase DNA methyltransferase Histone methyltransferase 5-Methyltetrahydrofolate- ...
... may refer to: 5-methyltetrahydrofolate-homocysteine methyltransferase reductase, a human gene Memory Type Range Registers ...
Changes to chromosome 5 include an extra segment of the short (p) or long (q) arm of the chromosome in each cell (partial ... Chromosome 5 spans about 182 million base pairs (the building blocks of DNA) and represents almost 6% of the total DNA in cells ... Chromosome 5 is the 5th largest human chromosome, yet has one of the lowest gene densities. This is partially explained by ... Chromosome 5 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. ...
... is one of two active coenzymes used by vitamin B12-dependent enzymes and is the specific vitamin B12 form used by 5- ... methyltetrahydrofolate-homocysteine methyltransferase (MTR), also known as methionine synthase.[citation needed] ...
82 (5): 941-950. doi:10.1007/s00253-009-1880-4. ISSN 1432-0614. PMID 19194700. S2CID 25880408. Bergey, D. H. (July 1919). " ... 145 (5): 1191-1199. doi:10.1099/13500872-145-5-1191. ISSN 1465-2080. PMID 10376835. Matsui, Tatsunobu; Yamada, Yukie; Mitsuya, ... 5-methyltetrahydrofolate-homocysteine methyltransferase, cadmium transporter and polynucleotide phosphorylase and are ...
Amtrak code 5-Methyltetrahydrofolate-homocysteine methyltransferase Mavalli Tiffin Room, an Indian food company MTR Foods ...
Protein arginine methyltransferase 6 PRXL2B: encoding protein Peroxiredoxin like 2B PSRC1: Proline/serine-rich coiled-coil ... 11 (5): 206. doi:10.1186/gb-2010-11-5-206. PMC 2898077. PMID 20441615. "Statistics & Downloads for chromosome 1". HUGO Gene ... 5-azacytidine type, common, fra(1)(q12) G0S2: encoding G0/G1 switch 2 GAS5 (1q25) GBA: glucosidase, beta; acid (includes ... TRE-CTC1-5: Transfer RNA-Glu (CTC) 1-5 UAP1: UDP-N-acetylhexosamine pyrophosphorylase USH2A: Usher syndrome 2A (autosomal ...
"Transfer of the methyl group from N5-methyltetrahydrofolates to homocysteine in Escherichia coli" (Free full text). The ... Other names in common use include tetrahydropteroyltriglutamate methyltransferase, homocysteine methylase, methyltransferase, ... homocysteine methyltransferase, cobalamin-independent methionine synthase, methionine synthase (cobalamin-independent), and ... Homocysteine is coordinated to a zinc ion, as initially suggested by spectroscopy and mutagenesis . Pejchal R, Ludwig ML ( ...
Other cobalamin-requiring methyltransferase enzymes are also known in bacteria, such as Me-H4-MPT, coenzyme M methyltransferase ... van der Put NM, van Straaten HW, Trijbels FJ, Blom HJ (April 2001). "Folate, homocysteine and neural tube defects: an overview ... Methyltransferases Methyl (-CH3) group transfers between two molecules. These use the MeB12 (methylcobalamin) form of the ... Methionine synthase, coded by MTR gene, is a methyltransferase enzyme which uses the MeB12 and reaction type 2 to transfer a ...
... that homocysteine can also be converted to methionine by the folate-independent enzyme betaine-homocysteine methyltransferase ( ... and recommended supplementation of methyltetrahydrofolate to potentially prevent and treat dementia (along with depression). A ... 677TT (but not 677CC/CT) individuals with lower plasma folate levels are at risk for elevated plasma homocysteine levels. In ... It does not result in thermolabile MTHFR and does not appear to affect homocysteine levels. It does, however, affect the ...
... histamine N-methyltransferase MeSH D08.811.913.555.500.625 - homocysteine S-methyltransferase MeSH D08.811.913.555.500.645 - 5- ... methyltetrahydrofolate-homocysteine s-methyltransferase MeSH D08.811.913.555.500.650 - nicotinamide N-methyltransferase MeSH ... betaine-homocysteine S-methyltransferase MeSH D08.811.913.555.500.250 - catechol O-methyltransferase MeSH D08.811.913.555. ... histone-lysine n-methyltransferase MeSH D08.811.913.555.500.800.650 - o-6-methylguanine-DNA methyltransferase MeSH D08.811. ...
This process, catalyzed by enzymes such as caffeoyl-CoA O-methyltransferase, is a key reaction in the biosynthesis of lignols, ... Methionine synthase regenerates methionine (Met) from homocysteine (Hcy). The overall reaction transforms 5- ... methyltetrahydrofolate (N5-MeTHF) into tetrahydrofolate (THF) while transferring a methyl group to Hcy to form Met. Methionine ... The formation of Me-CpG is catalyzed by the enzyme DNA methyltransferase. In vertebrates, DNA methylation typically occurs at ...
S-adenosyl-L-homocysteine + sarcosine Thus, the substrates of this enzyme are S-adenosyl methionine and glycine, whereas its ... Glycine N-methyltransferase belongs to the family of methyltransferase enzymes. The systematic name of this enzyme class is S- ... Other names in common use include glycine methyltransferase, S-adenosyl-L-methionine:glycine methyltransferase, and GNMT. This ... In enzymology, a glycine N-methyltransferase (EC 2.1.1.20) is an enzyme that catalyzes the chemical reaction S-adenosyl-L- ...
... can be recycled into methionine. This process uses N5-methyl tetrahydrofolate as the methyl donor and cobalamin ( ... DNA methyltransferase as an intermediate acceptor in the process of DNA methylation). The adenosine is then hydrolyzed to yield ... Wikiversity has learning resources about Homocysteine Homocysteine MS Spectrum Homocysteine at Lab Tests Online Homocysteine: ... Homocysteine also acts as an allosteric antagonist at Dopamine D2 receptors. It has been proposed that both homocysteine and ...
Homocysteine is an intermediate that is responsible for maintaining methylation reactions in critical metabolic processes. It ... Recent studies have shown that diabetic patients have decreased H3K9me3 and an increase in the Histone methyltransferase called ... This reaction is a critical step in the conversion of homocysteine to methionine. The resulting product is a methyl donor that ... After examining Type 2 diabetes patients, it was found that levels of homocysteine were exceptionally high when compared to ...
Additionally, a defect in homocysteine methyltransferase or a deficiency of vitamin B12 may lead to a so-called "methyl-trap" ... measured as methyltetrahydrofolate (in practice, "folate" refers to all derivatives of folic acid, but methylhydrofolate is the ... Plasma total homocysteine is only measured in special circumstances. A level above 15 μmol/L could be indicative of a folate ... High homocysteine levels in the blood can lead to vascular injuries by oxidative mechanisms which can contribute to cerebral ...
This is hydrolysed to homocysteine and adenosine by S-adenosylhomocysteine hydrolase EC 3.3.1.1 and the homocysteine recycled ... DNA methyltransferase SAM-I riboswitch SAM-II riboswitch SAM-III riboswitch SAM-IV riboswitch SAM-V riboswitch SAM-VI ... that use SAM as a substrate produce S-adenosyl homocysteine as a product. S-Adenosyl homocysteine is a strong negative ... Methyltransferases are also responsible for the addition of methyl groups to the 2′ hydroxyls of the first and second ...
... in a reaction catalyzed by homocysteine methyltransferase, to methionine. A defect in homocysteine methyltransferase or a ... methyltetrahydrofolate (5-MTHF), a direct target of methyl donors such as S-adenosyl methionine (SAMe), recycles the inactive ... Increased homocysteine levels suggest tissue folate deficiency, but homocysteine is also affected by vitamin B12 and vitamin B6 ... Conversion of homocysteine to methionine requires folate and vitamin B12. Elevated plasma homocysteine and low folate are ...
... histamine N-methyltransferase EC 2.1.1.9: thiol S-methyltransferase EC 2.1.1.10: homocysteine S-methyltransferase EC 2.1.1.11: ... betaine-homocysteine S-methyltransferase EC 2.1.1.6: catechol O-methyltransferase EC 2.1.1.7: nicotinate N-methyltransferase EC ... EC 2.1.1.1: nicotinamide N-methyltransferase EC 2.1.1.2: guanidinoacetate N-methyltransferase EC 2.1.1.3: thetin-homocysteine S ... phenol O-methyltransferase EC 2.1.1.26: iodophenol O-methyltransferase EC 2.1.1.27: tyramine N-methyltransferase EC 2.1.1.28: ...
5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase. On-line free medical diagnosis assistant. Ranked list of possible ... 5 months ago ... Any Dr.s that you can recammend in the NY CT area that do similiar testing .... youtube.com - Fri, 12 Jul 2013 ... 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase. Folate and Methylation Defects and Metabolism in .... ...
Homocysteine-methyl tetrahydrofolate methyltransferase. *METH_HUMAN. *Methionine Synthase. *Tetrahydropteroylglutamate ... Some of the excess homocysteine is excreted in urine. Researchers have not determined how altered levels of homocysteine and ... Without functional methionine synthase, homocysteine cannot be converted to methionine. As a result, homocysteine builds up in ... Carmel R, Green R, Rosenblatt DS, Watkins D. Update on cobalamin, folate, and homocysteine. Hematology Am Soc Hematol Educ ...
Methyltransferase Arakawas syndrome II Betaine-homocysteine S-methyltransferase GRCh38: Ensembl release 89: ENSG00000116984 - ... "Methionine synthase exists in two distinct conformations that differ in reactivity toward methyltetrahydrofolate, ... The cob-independent MetE consists of two TIM-barrel domains that bind homocysteine and N5-MeTHF individually. The two domains ... March 2003). "Homocysteine remethylation enzyme polymorphisms and increased risks for neural tube defects". Molecular Genetics ...
Plasma homocysteine and genetic variants of homocysteine metabolism enzymes in patients from central Greece with primary open- ... Failure to confirm influence of methyltetrahydrofolate reductase (MTHFR) polymorphisms on age at onset of Huntington disease. ... PMID 21567207] Tetra primer ARMS-PCR relates folate/homocysteine pathway genes and ACE gene polymorphism with coronary artery ... PMID 25074646] Associations of Common Variants in Methionine Metabolism Pathway Genes with Plasma Homocysteine and the Risk of ...
1e). Abundant PFAM domains in Hcoe-symbiont peptides include antioxidants (glutaredoxin, thioredoxin), methyltransferases, and ... Different e-value cutoffs (1 × 10−4,, 1 × 10−5, 1 × 10−8, 1 × 10−10) were examined and the cutoff that resulted in a minimum ... H. coerulea from the Andaman Sea, in the northeastern Indian Ocean, hosts thermally tolerant symbionts of ITS2 type D2-4-542, ... Orthologous gene groups were identified using OrthoMCL with default settings (e-value cutoff 1 × 10−5, protein identity 50%, ...
The accumulation of homocysteine leads to damage of the collagen and elastic fibers. The binding of homocysteine to lysine ... Glycine N -methyltransferase deficiency: a new patient with a novel mutation. J Inherit Metab Dis. 2003. 26(8):745-59. [QxMD ... Homocysteine is readily oxidized in plasma to form homocystine- and homocysteine-mixed disulfides. This oxidation has been ... Homocysteine has been found to induce neurological dysfunction via oxidative stress. The cytotoxicity of homocysteine has been ...
"Transfer of the methyl group from N5-methyltetrahydrofolates to homocysteine in Escherichia coli" (Free full text). The ... Other names in common use include tetrahydropteroyltriglutamate methyltransferase, homocysteine methylase, methyltransferase, ... homocysteine methyltransferase, cobalamin-independent methionine synthase, methionine synthase (cobalamin-independent), and ... Homocysteine is coordinated to a zinc ion, as initially suggested by spectroscopy and mutagenesis . Pejchal R, Ludwig ML ( ...
... homocysteine methyltransferase. 28.91. 0.7663. 18. slr1163 Unknown protein. 33.05. 0.7792. 19. slr2119 Unknown protein. 33.27. ...
homocysteine S-methyltransferase. 7e-21. 100. NC_011837:950000:982629. 982629. 985034. 2406. Clostridium kluyveri NBRC 12016, ... homocysteine S-methyltransferase. 7e-35. 147. NC_018867:2063741:2075761. 2075761. 2076423. 663. Dehalobacter sp. CF chromosome ... homocysteine methyltransferase. 2e-11. 69.3. NC_014666:3629696:3629696. 3629696. 3633406. 3711. Frankia sp. EuI1c chromosome, ... homocysteine methyltran sferase-cobalamin binding domain. 4e-09. 61.2. NC_007681:218921:231535. 231535. 232374. 840. ...
... homocysteine methyltransferase. 249.99. 0.5380. 190. sll1222 Hypothetical protein. 252.76. 0.5148. 191. ssl1911 Glutamine ...
PRMT6: Protein arginine methyltransferase 6. *PSRC1: Proline/serine-rich coiled-coil protein 1 ... doi:10.1186/gb-2010-11-5-206. PMC 2898077. PMID 20441615.. *↑ "Statistics & Downloads for chromosome 1". HUGO Gene Nomenclature ... Chromosome 1 spans about 249 million nucleotide base pairs, which are the basic units of information for DNA.[5] It represents ... FRA1J encoding protein Fragile site, 5-azacytidine type, common, fra(1)(q12) ...
... homocysteine methyltransferase (NCBI). 32, 135. RSP_3347. RSP_3347. methionine synthase, 5-methyltetrahydrofolate--homocysteine ... POSITION A C G T 1 1.0 0.0 0.0 0.0 2 0.2 0.0 0.4 0.4 3 0.0 0.0 0.8 0.2 4 0.8 0.0 0.2 0.0 5 0.0 0.0 0.0 1.0 6 0.0 0.0 1.0 0.0 7 ... POSITION A C G T 1 0.0 0.0 0.0 1.0 2 0.0 0.0 1.0 0.0 3 0.0 0.0 1.0 0.0 4 0.0 0.0 0.0 1.0 5 0.0 1.0 0.0 0.0 6 0.0 0.0 0.0 1.0 7 ... POSITION A C G T 1 1.0 0.0 0.0 0.0 2 0.25 0.0 0.75 0.0 3 1.0 0.0 0.0 0.0 4 1.0 0.0 0.0 0.0 5 0.0 0.0 0.75 0.25 6 0.0 0.0 1.0 ...
... homocysteine methyltransferase, MetH *. Mycobacterium smegmatis str. MC2 155 Site: position = -94. score = 23.13 sequence = ... Gene: MAB_2129: 5-methyltetrahydrofolate--homocysteine methyltransferase, MetH 5-methyltetrahydrofolate--homocysteine ...
... homocysteine methyltransferase (NCBI ptt file). 318, 338. BC4251. BC4251. 5-methyltetrahydrofolate--homocysteine ... Uroporphyrin-III C-methyltransferase (NCBI ptt file). 338, 514. BC1684. BC1684. ABC transporter ATP-binding protein (NCBI ptt ... POSITION A C G T 1 0.2 0.0 0.8 0.0 2 0.2 0.0 0.6 0.2 3 0.2 0.6 0.0 0.2 4 0.8 0.2 0.0 0.0 5 0.2 0.8 0.0 0.0 6 0.0 0.0 1.0 0.0 7 ... POSITION A C G T 1 0.0 1.0 0.0 0.0 2 0.0 1.0 0.0 0.0 3 0.0 0.0 0.0 1.0 4 0.5 0.0 0.0 0.5 5 0.5 0.0 0.0 0.5 6 0.0 0.0 1.0 0.0 7 ...
... homocysteine methyltransferase (EC 2.1.1.13) Locus tag: ATW7_10323. Name: metH. Funciton: 5-methyltetrahydrofolate-- ...
Catechol O methyltransferase Cartoon diagram of human COMT in complex with 3,5 dinitrocatechol (dark blue) and S adenosyl ... Catechol-O-methyl transferase. Homocysteine. Betaine-homocysteine methyltransferase - Homocysteine methyltransferase - ... methyltransferase activity. • O-methyltransferase activity. • catechol O-methyltransferase activity. • transferase activity. ... Phosphatidyl ethanolamine methyltransferase - DNMT3B - Histone methyltransferase - Thymidylate synthase - DNA methyltransferase ...
T genotype with plasma homocysteine levels was weakened by other factors that impact homocysteine levels. The effect of MTHFR c ... and triglycerides with plasma homocysteine levels and with the following 7 variants of homocysteine metabolism: dihydrofolate ... Polymorphisms of homocysteine metabolism are associated with intracranial aneurysms. Semmler, Alexander; Linnebank, Michael; ... Moreover, the G allele of Tc2 c.776Câ G was associated with higher homocysteine plasma levels in the subgroup of patients (p = ...
... and its functions were confirmed by methyltransferase activity analysis and electrophoretic mobility shift assays. The minimum ... The gene encoding ArsR/methyltransferase fusion protein, arsRM, was amplified and expressed in Escherichia coli BL21 (DE3), and ... prediction analyses suggested that ArsRM is a difunctional protein with transcriptional regulation and methyltransferase ... One unit of methyltransferase activity was defined as the amount of enzyme that generated 1.0 µmol of S-adenosyl homocysteine ...
5-methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR) , and serine hydroxymethyltransferase (SHMT1) and ... betaine-homocysteinemethyltransferase (BHMT) , 5-methyltetrahydrofolate-homocysteine (MTR), 5-methyltetrahydrofolate- ... homocysteine methyltransferase reductase (MTRR) , and serine hydroxymethyltransferase (SHMT1) and folate receptor 1 (FOLR1) ...
Pajares, M. A., and Pérez-Sala, D. (2006). Betaine homocysteine S-methyltransferase: Just a regulator of homocysteine ... homocysteine; MET, methionine; methylene-THF, N5,10-methylene tetrahydrofolate; methyl-THF, N5-methyl tetrahydrofolate; SAH, S- ... The second enzyme, betaine-homocysteine methyltransferases (BHMT), has two isoforms, of which one is expressed only in the ... Methionine can also acquire a methyl group from betaine via a reaction involving betaine homocysteine methyl-transferases (BHMT ...
Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ... Now available in a cost efficient pack of 5 plates of 96 wells each, conveniently packed along with the other reagents in 5 ... Human MIP5(Macrophage Inflammatory Protein 5) ELISA Kit. *Human MITF(Microphthalmia Associated Transcription Factor) ELISA Kit ...
Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ...
Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ...
Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ...
Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ...
Human DNMT3A(DNA Methyltransferase 3A) ELISA Kit. *Human DPAGT1(Dolichyl Phosphate-N-Acetylglucosaminephosphotransferase 1) ... Human OASL(2′,5′-Oligoadenylate Synthetase Like Protein) ELISA Kit. *Human OSBPL8(Oxysterol Binding Protein Like Protein 8) ... Human MIP5(Macrophage Inflammatory Protein 5) ELISA Kit. *Human MITF(Microphthalmia Associated Transcription Factor) ELISA Kit ...
... and can be measured clinically as an increased homocysteine level in vitro. Increased homocysteine can also be caused by a ... THF may be produced in the conversion of homocysteine to methionine, or may be obtained in the diet. It is converted by a non-B ... but now mainly as an elevation of homocysteine in the blood and urine (homocysteinuria). This condition may result in long term ... but not the elevated levels of homocysteine, which is normally converted to methionine by MTR. ...
  • As part of this regulation, homocysteine is re-methylated to methionine via two different routes requiring either methionine synthase or betaine-homocysteine methyltransferase. (stackexchange.com)
  • An alternative remethylation pathway also exists using the cobalamin independent betaine-homocysteine methyltransferase. (bmj.com)
  • In remethylation pathway, Hcy can be remethylated to form Met via methionine synthase (MS) or betaine-homocysteine methyltransferase (BHMT), in which cofactors such as folic acid and vitamin B 12 or betaine are required. (hindawi.com)
  • Both the cobalamin-dependent and cobalamin-independent forms of the enzyme carry out the same overall chemical reaction, the transfer of a methyl group from 5-methyltetrahydrofolate (N5-MeTHF) to homocysteine, yielding tetrahydrofolate (THF) and methionine. (wikipedia.org)
  • Methionine synthase obtains the required methyl group from 5-methyltetrahydrofolate in a vitamin B 12 (actually methylcobalamin)-dependent reaction. (stackexchange.com)
  • 1 By receiving a methyl group from 5′-methyltetrahydrofolate, it is reconverted to methionine (fig 1), which is essential for many biochemical reactions critical to the formation of protein, nucleic acids, and creatinine. (bmj.com)
  • Simplified picture showing homocysteine involvement in different metabolic pathways, as well as the role of vitamins B-6, B-12, and folate as a co-factors in this pathway. (medscape.com)
  • Folate and vitamin B-12 are required for the remethylation of homocysteine to methionine. (medscape.com)
  • Homocysteine is a sulphur containing amino acid that plays an important role in methionine and folate metabolism. (bmj.com)
  • The variant methylenetetrahydrofolate reductase (MTHFR) C677T is associated with elevated homocysteine levels, cardiovascular disease and stroke, which supports a causal relationship between hyperhomocysteinemia and vascular disease. (bvsalud.org)
  • This should help answer the question: how to people without problematic genetic variants avoid problems associated with elevated homocysteine levels (most notably arteriosclerosis)? (radicalhealing.info)
  • The cobalamin is then demethylated by zinc-activated thiolate homocysteine, generating methionine and reducing the cofactor to a Cob(I) state. (wikipedia.org)
  • When in the Cob(I) form, the enzyme-bound cofactor is now able to abstract a methyl group from activated 5-methyltetrahydrofolate (N5-MeTHF), yielding tetrahydrofolate (THF) and regenerating the methylcoalamin form of the enzyme. (wikipedia.org)
  • In mammals PNMT is just one member of a large family of methyltransferases which use S -adenosylmethionine (AdoMet) as a cofactor to provide a methyl group. (stackexchange.com)
  • Failure to confirm influence of methyltetrahydrofolate reductase (MTHFR) polymorphisms on age at onset of Huntington disease. (snpedia.com)
  • For those with MTHFR polymorphisms it is important to supplement with a L-5-MTHF supplement. (radicalhealing.info)
  • Correlation between methyltetrahydrofolate reductase (MTHFR) polymorphisms and isolated patent ductus arteriosus in Taiwan. (cdc.gov)
  • The remethylation pathway comprises 2 intersecting biochemical pathways and results in the transfer of a methyl group (CH 3 ) to homocysteine from methylcobalamin, which receives its methyl group from S-adenosylmethionine (SAM), from 5-methyltetrahydrofolate (an active form of folic acid), or from betaine (trimethylglycine). (medscape.com)
  • The frequent 5,10-methylenetetrahydrofolate reductase C677T polymorphism is associated with a common haplotype in whites, Japanese, and Africans. (snpedia.com)
  • The observation that methylenetetrahydrofolate reductase is increased in hyperthyroidism and decreased in hypothyroidism may be relevant to the relationship between plasma homocysteine levels and thyroid status. (medscape.com)
  • Remethylation requires 5, 10-methylenetetrahydrofolate reductase and methionine synthase. (bmj.com)
  • Homocysteine is metabolized by means of 2 pathways: remethylation and transsulfuration. (medscape.com)
  • The transsulfuration pathway of methionine/homocysteine degradation produces the amino acids cysteine and taurine. (medscape.com)
  • The underlying enzymological abnormality, a deficit of cystathionine β synthase, results in impairment of homocysteine transsulfuration. (bmj.com)
  • It is concluded that quercetin reduces serum homocysteine by increasing remethylation and transsulfuration of homocysteine in rats exposed to a methionine-enriched diet. (hindawi.com)
  • When pyridoxine supplementation was initiated at age 18 years, the patient's plasma homocysteine levels decreased below the reference range. (medscape.com)
  • At age 50 years, the patient's plasma homocysteine levels still remained low. (medscape.com)
  • T is the most prevalent known genetic cause of elevated plasma homocysteine levels, but the association of this allele with vascular disease has been controversial. (bvsalud.org)
  • Without functional methionine synthase, homocysteine cannot be converted to methionine. (medlineplus.gov)
  • Pathways for the metabolism of homocysteine. (bmj.com)
  • Conversion of S-adenosyl-L-homocysteine (SAH) to homocysteine increased and the metabolism of homocysteine was reduced under diabetic conditions, and consequently homocysteine accumulated in the elimination phase. (biomedcentral.com)
  • Urine methionine and homocysteine levels are elevated because of deficient levels of cystathionine beta-synthase. (medscape.com)
  • Although alterations in the methionine metabolism cycle (MMC) have been associated with vascular complications of diabetes, there have not been consistent results about the levels of methionine and homocysteine in type 2 diabetes mellitus (T2DM). (biomedcentral.com)
  • The aim of the current study was to predict changes in plasma methionine and homocysteine concentrations after simulated consumption of methionine-rich foods, following the development of a mathematical model for MMC in Zucker Diabetic Fatty (ZDF) rats, as a representative T2DM animal model. (biomedcentral.com)
  • Using our model, we performed simulations to compare the changes in plasma methionine and homocysteine concentrations between ZDF and normal rats, by multiple administrations of the methionine-rich diet of 1 mmol/kg, daily for 60 days. (biomedcentral.com)
  • The levels of methionine and homocysteine were elevated approximately two- and three-fold, respectively, in ZDF rats, while there were no changes observed in the normal control rats. (biomedcentral.com)
  • These results can be interpreted to mean that both methionine and homocysteine will accumulate in patients with T2DM, who regularly consume high-methionine foods. (biomedcentral.com)
  • Here, we focused on the fact that a high-fat diet affects the metabolism of both methionine and homocysteine in a diabetic rat model [ 14 ]. (biomedcentral.com)
  • Nicotinamide N-Methyltransferase" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . (ouhsc.edu)
  • This graph shows the total number of publications written about "Nicotinamide N-Methyltransferase" by people in this website by year, and whether "Nicotinamide N-Methyltransferase" was a major or minor topic of these publications. (ouhsc.edu)
  • Below are the most recent publications written about "Nicotinamide N-Methyltransferase" by people in Profiles. (ouhsc.edu)
  • The mechanism of the cobalamin-independent (MetE) form, by contrast, proceeds through a direct methyl transfer from the activated N5-MeTHF to zinc thiolate homocysteine. (wikipedia.org)
  • Cobalamin-independent methionine synthase (MetE) catalyzes the synthesis of methionine by a direct transfer of the methyl group of N5-methyltetrahydrofolate (CH3-H2PteGlun) to the sulfur atom of homocysteine (Hcy). (rcsb.org)
  • In humans, catechol- O -methyltransferase protein is encoded by the COMT gene . (en-academic.com)
  • The gene encoding ArsR/methyltransferase fusion protein, arsR M , was amplified and expressed in Escherichia coli BL21 (DE3), and this strain showed resistance to arsenic in the present of 0.25-6 mM As(III), aresenate, or pentavalent roxarsone. (biomedcentral.com)
  • Functional prediction analyses suggested that ArsR M is a difunctional protein with transcriptional regulation and methyltransferase activities. (biomedcentral.com)
  • mete2_orysj : 81.6)","protein_coding" "MA_520939g0010","No alias","Picea abies","5-methyltetrahydropteroyltriglutamate--homocysteine methyltransferase 1 OS=Oryza sativa subsp. (ntu.edu.sg)
  • This pathway is dependent on adequate intake of vitamin B-6 and the hepatic conversion of vitamin B-6 into its active form, pyridoxal-5'-phosphate (P5P). (medscape.com)
  • The amino acid serine, which is a downstream metabolite generated from betaine via the homocysteine remethylation pathway is another necessary step. (medscape.com)
  • As a universal key intermediate in the MMC, homocysteine is not obtained from the diet, but is remethylated to methionine, or converted to cysteine by the trans-sulfuration pathway. (biomedcentral.com)
  • This study was aimed at investigating the effects of quercetin on mRNA expression and activity of critical enzymes in homocysteine metabolism in rats fed a methionine-enriched diet. (hindawi.com)
  • Here are 6 enzymes, the first 3 directly convert homocysteine to other amino acids, the other 3 listed here are enzymes which a deficiency of will limit one of those conversions. (radicalhealing.info)
  • Researchers have not determined how altered levels of homocysteine and methionine lead to the health problems associated with homocystinuria. (medlineplus.gov)
  • Homocystinuria represents a group of hereditary metabolic disorders characterized by an accumulation of homocysteine in the serum and an increased excretion of homocysteine in the urine. (medscape.com)
  • About 10 years after the discovery of homocystinuria it was hypothesised by McCully 4 that high plasma homocysteine might be causally related to the vascular complications of the disease. (bmj.com)
  • In 1976, Wilcken and Wilcken 5 studied patients without homocystinuria but with angiographically proved coronary artery disease. (bmj.com)
  • Association between 5,10-methylenetetrahydrofolate, gene polymorphism and congenital heart disease. (cdc.gov)
  • Homocysteine concentrations are higher in postmenopausal women than in premenopausal women. (medscape.com)
  • As a consequence, the concentrations of the amino acid in plasma may rise 20-fold from the normative range of 5-15 μmol/l. (bmj.com)
  • Using the methionine loading test, in which 0.1 mg/kg body weight of this amino acid is administered orally, they found that the prevalence of high circulating homocysteine concentrations, or hyperhomocysteinaemia, was higher than in normal controls. (bmj.com)
  • Maternal genetic effects, exerted by genes involved in homocysteine remethylation, influence the risk of spina bifida. (medlineplus.gov)
  • What is the relationship between Homocysteine and Norepinephrine metabolic cycles? (stackexchange.com)
  • Homocysteine is actually a by product of certain normal metabolic amino acid breakdown and processing. (ecopolitan.com)
  • Thus, 0we hypothesized that long-term administration of a high-methionine diet to T2DM rats with normal renal function may create metabolic changes, culminating in an elevated level of circulating homocysteine. (biomedcentral.com)
  • Serum homocysteine was significantly increased after methionine treatment and decreased after the addition of quercetin. (hindawi.com)
  • Specifically, methionine synthase carries out a chemical reaction that converts the amino acid homocysteine to another amino acid called methionine. (medlineplus.gov)
  • In enzymology, a 5-methyltetrahydropteroyltriglutamate-homocysteine S-methyltransferase (EC 2.1.1.14) is an enzyme that catalyzes the chemical reaction 5-methyltetrahydropteroyltri-L-glutamate + L-homocysteine ⇌ {\displaystyle \rightleftharpoons } tetrahydropteroyltri-L-glutamate + L-methionine Thus, the two substrates of this enzyme are 5-methyltetrahydropteroyltri-L-glutamate and L-homocysteine, whereas its two products are tetrahydropteroyltri-L-glutamate and L-methionine. (wikipedia.org)
  • This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. (wikipedia.org)
  • These methyltransferases are involved in a very diverse set of pathways including the synthesis of nucleic acids and of certain phospholipids, as well as the methylation of DNA and histones. (stackexchange.com)
  • PURPOSE: The role of homocysteine in the pathogenesis of arteriosclerosis and stroke is under debate. (bvsalud.org)
  • METHODS: Fifteen-week-old rats were irradiated with a dose of 5 or 10 Gy on four consecutive days, resulting in a cumulative dose in opposing fields of 20 Gy (n = 15) and 40 Gy (n = 17), respectively. (bvsalud.org)
  • In humans it is encoded by the MTR gene (5-methyltetrahydrofolate-homocysteine methyltransferase). (wikipedia.org)
  • CONCLUSION: These data support the hypothesis that alterations in homocysteine metabolism and an unfavorable blood lipoprotein profile may have a common genetic basis. (bvsalud.org)
  • To verify this hypothesis, mathematical modeling of methionine metabolism was required to predict the levels of homocysteine derived from given amounts of methionine. (biomedcentral.com)
  • In a previous post we looked at Biotin (vitamin B7) and we saw that while biotin/biotinidase deficiency is technically extremely rare, a partial deficiency seems to exist in about 5% of people with autism. (epiphanyasd.com)
  • DL-homocysteine inhibits the production of tyrosinase, which is the major pigment enzyme. (medscape.com)
  • The systematic name of this enzyme class is 5-methyltetrahydropteroyltri-L-glutamate:L-homocysteine S-methyltransferase. (wikipedia.org)
  • Catechol- O -methyltransferase is involved in the inactivation of the catecholamine neurotransmitters ( dopamine , epinephrine , and norepinephrine ). (en-academic.com)
  • The diagram appears to state that Dopamine gets converted to Norepinephrine , which gets converted to Epinephrine, and as a side effect, Homocysteine cycle gets advanced too (or is it involved? (stackexchange.com)
  • Norepinephrine is converted to epinephrine by phenylethanolamine N -methyltransferase (PNMT). (stackexchange.com)
  • Moreover, the G allele of Tc2 c.776Câ G was associated with higher homocysteine plasma levels in the subgroup of patients (p = 0.013, 1-way ANOVA). (bvsalud.org)
  • It is important to determine the interplay of factors that influence homocysteine plasma levels, such as age, gender, smoking and the genetic background. (bvsalud.org)
  • Women tend to have lower basal levels of homocysteine than do men, and neither contraceptives nor hormone replacement therapy seems to significantly alter the levels. (medscape.com)
  • 2009) Glycine N -methyltransferase and regulation of S -adenosylmethionine levels. (stackexchange.com)
  • In conclusion, my answer to your question is that it is unlikely that stress leads to elevated levels of homocysteine as long as all of the relevant regulatory machinery is functioning correctly. (stackexchange.com)
  • If there is a problem with homocysteine recycling then yes, homocysteine levels would rise, but given that there so many AdoMet-dependent methylation reactions it is unclear how big a contribution PNMT would make to the overall homocysteine load. (stackexchange.com)
  • Transfer of the methyl group from N5-methyltetrahydrofolates to homocysteine in Escherichia coli" (Free full text). (wikipedia.org)
  • BACKGROUND/AIM: Recent studies have suggested a relation of homocysteine with lipid metabolism. (bvsalud.org)
  • By what mechanism does elevated homocysteine level cause endothelial dysfunction and damage? (stackexchange.com)
  • By what mechanism does elevated homocysteine level accelerate thrombin formation? (stackexchange.com)
  • The methylation activity and regulatory action of ArsR M were analyzed using Discovery Studio 2.0, and its functions were confirmed by methyltransferase activity analysis and electrophoretic mobility shift assays. (biomedcentral.com)