Purine Nucleotides: Purines attached to a RIBOSE and a phosphate that can polymerize to form DNA and RNA.Purines: A series of heterocyclic compounds that are variously substituted in nature and are known also as purine bases. They include ADENINE and GUANINE, constituents of nucleic acids, as well as many alkaloids such as CAFFEINE and THEOPHYLLINE. Uric acid is the metabolic end product of purine metabolism.Nucleotides: The monomeric units from which DNA or RNA polymers are constructed. They consist of a purine or pyrimidine base, a pentose sugar, and a phosphate group. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Purine Nucleosides: Purines with a RIBOSE attached that can be phosphorylated to PURINE NUCLEOTIDES.Inosine Monophosphate: Inosine 5'-Monophosphate. A purine nucleotide which has hypoxanthine as the base and one phosphate group esterified to the sugar moiety.Amidophosphoribosyltransferase: An enzyme, involved in the early steps of purine nucleotide biosynthesis, that catalyzes the formation of 5-phosphoribosylamine from glutamine and phosphoribosylpyrophosphate. EC 184.108.40.206.Adenine NucleotidesPhosphoribosyl Pyrophosphate: The key substance in the biosynthesis of histidine, tryptophan, and purine and pyrimidine nucleotides.Ribose-Phosphate Pyrophosphokinase: An enzyme that catalyzes the formation of phosphoribosyl pyrophosphate from ATP and ribose-5-phosphate. EC 220.127.116.11.Pyrimidine Nucleotides: Pyrimidines with a RIBOSE and phosphate attached that can polymerize to form DNA and RNA.AMP Deaminase: An enzyme that catalyzes the deamination of AMP to IMP. EC 18.104.22.168.Nucleotide Deaminases: Catalyze the hydrolysis of nucleotides with the elimination of ammonia.Guanine NucleotidesHypoxanthines: Purine bases related to hypoxanthine, an intermediate product of uric acid synthesis and a breakdown product of adenine catabolism.Adenylosuccinate Lyase: An enzyme that, in the course of purine ribonucleotide biosynthesis, catalyzes the conversion of 5'-phosphoribosyl-4-(N-succinocarboxamide)-5-aminoimidazole to 5'-phosphoribosyl-4-carboxamide-5-aminoimidazole and the conversion of adenylosuccinic acid to AMP. EC 22.214.171.124.Inosine NucleotidesPurine-Nucleoside Phosphorylase: An enzyme that catalyzes the reaction between a purine nucleoside and orthophosphate to form a free purine plus ribose-5-phosphate. EC 126.96.36.199.Hypoxanthine: A purine and a reaction intermediate in the metabolism of adenosine and in the formation of nucleic acids by the salvage pathway.Adenylosuccinate Synthase: A carbon-nitrogen ligase. During purine ribonucleotide biosynthesis, this enzyme catalyzes the synthesis of adenylosuccinate from GTP; IMP; and aspartate with the formation of orthophosphate and GDP. EC 188.8.131.52.Inosine: A purine nucleoside that has hypoxanthine linked by the N9 nitrogen to the C1 carbon of ribose. It is an intermediate in the degradation of purines and purine nucleosides to uric acid and in pathways of purine salvage. It also occurs in the anticodon of certain transfer RNA molecules. (Dorland, 28th ed)Hypoxanthine Phosphoribosyltransferase: An enzyme that catalyzes the conversion of 5-phosphoribosyl-1-pyrophosphate and hypoxanthine, guanine, or 6-mercaptopurine to the corresponding 5'-mononucleotides and pyrophosphate. The enzyme is important in purine biosynthesis as well as central nervous system functions. Complete lack of enzyme activity is associated with the LESCH-NYHAN SYNDROME, while partial deficiency results in overproduction of uric acid. EC 184.108.40.206.Ribonucleotides: Nucleotides in which the purine or pyrimidine base is combined with ribose. (Dorland, 28th ed)Molecular Sequence Data: 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.Adenosine Triphosphate: An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.Adenine: A purine base and a fundamental unit of ADENINE NUCLEOTIDES.Methylthioinosine: 6-(Methylthio)-9-beta-D-ribofuranosylpurine. An analog of inosine with a methylthio group replacing the hydroxyl group in the 6-position.Phosphoribosylaminoimidazolecarboxamide Formyltransferase: An enzyme that catalyzes the conversion of aminoimidazole-4-carboxamide ribonucleotide to 5-formyl-aminoimidazole-4-carboxamide ribonucleotide in the purine de novo synthesis pathway. It requires the cofactor N(10)-FORMYLTETRAHYDROFOLATE as the formyl donor.Pentosyltransferases: Enzymes of the transferase class that catalyze the transfer of a pentose group from one compound to another.PentosephosphatesGMP Reductase: An enzyme that catalyzes the reversible oxidation of inosine 5'-phosphate (IMP) to guanosine 5'-phosphate (GMP) in the presence of AMMONIA and NADP+. This enzyme was formerly classified as EC 220.127.116.11.Adenosine Monophosphate: Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position.Guanosine Triphosphate: Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.Ribonucleosides: Nucleosides in which the purine or pyrimidine base is combined with ribose. (Dorland, 28th ed)Azaserine: Antibiotic substance produced by various Streptomyces species. It is an inhibitor of enzymatic activities that involve glutamine and is used as an antineoplastic and immunosuppressive agent.Guanosine Monophosphate: A guanine nucleotide containing one phosphate group esterified to the sugar moiety and found widely in nature.Purine-Pyrimidine Metabolism, Inborn ErrorsBase Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.5,10-Methylenetetrahydrofolate Reductase (FADH2): 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 18.104.22.168 and 22.214.171.124.Acanthamoeba castellanii: A species of free-living soil amoebae in the family Acanthamoebidae. It can cause ENCEPHALITIS and KERATITIS in humans.Amino Acid Sequence: 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.Hydroxymethyl and Formyl Transferases: Enzymes that catalyze the transfer of hydroxymethyl or formyl groups. EC 2.1.2.Kinetics: The rate dynamics in chemical or physical systems.GuanineAminoimidazole Carboxamide: An imidazole derivative which is a metabolite of the antineoplastic agents BIC and DIC. By itself, or as the ribonucleotide, it is used as a condensation agent in the preparation of nucleosides and nucleotides. Compounded with orotic acid, it is used to treat liver diseases.Guanine Deaminase: An enzyme that catalyzes the deamination of guanine to form xanthine. EC 126.96.36.199.Lesch-Nyhan Syndrome: An inherited disorder transmitted as a sex-linked trait and caused by a deficiency of an enzyme of purine metabolism; HYPOXANTHINE PHOSPHORIBOSYLTRANSFERASE. Affected individuals are normal in the first year of life and then develop psychomotor retardation, extrapyramidal movement disorders, progressive spasticity, and seizures. Self-destructive behaviors such as biting of fingers and lips are seen frequently. Intellectual impairment may also occur but is typically not severe. Elevation of uric acid in the serum leads to the development of renal calculi and gouty arthritis. (Menkes, Textbook of Child Neurology, 5th ed, pp127)Polymorphism, Single Nucleotide: A single nucleotide variation in a genetic sequence that occurs at appreciable frequency in the population.IMP Dehydrogenase: An enzyme that catalyzes the dehydrogenation of inosine 5'-phosphate to xanthosine 5'-phosphate in the presence of NAD. EC 188.8.131.52.Sulfanilic Acids: Aminobenzenesulfonic acids. Organic acids that are used in the manufacture of dyes and organic chemicals and as reagents.Carbon-Nitrogen Ligases: Enzymes that catalyze the joining of two molecules by the formation of a carbon-nitrogen bond. EC 6.3.Escherichia coli: 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.Adenine Phosphoribosyltransferase: An enzyme catalyzing the formation of AMP from adenine and phosphoribosylpyrophosphate. It can act as a salvage enzyme for recycling of adenine into nucleic acids. EC 184.108.40.206.Adenosine: A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.Cloning, Molecular: 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.Uridine Triphosphate: Uridine 5'-(tetrahydrogen triphosphate). A uracil nucleotide containing three phosphate groups esterified to the sugar moiety.Xanthine: A purine base found in most body tissues and fluids, certain plants, and some urinary calculi. It is an intermediate in the degradation of adenosine monophosphate to uric acid, being formed by oxidation of hypoxanthine. The methylated xanthine compounds caffeine, theobromine, and theophylline and their derivatives are used in medicine for their bronchodilator effects. (Dorland, 28th ed)Adenosine Diphosphate: Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position.Guanosine Diphosphate: A guanine nucleotide containing two phosphate groups esterified to the sugar moiety.Ammonia: A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.Phosphoribosylglycinamide Formyltransferase: An enzyme that catalyzes the transfer of a formyl group from N10-formyltetrahydrofolate to N1-(5-phospho-D-ribosyl)glycinamide to yield N2-formyl-N1-(5-phospho-D-ribosyl)glycinamide and tetrahydrofolate. It plays a role in the de novo purine biosynthetic pathway.Mutation: 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.Adenosine Deaminase: An enzyme that catalyzes the hydrolysis of ADENOSINE to INOSINE with the elimination of AMMONIA.DNA: 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).Mitochondrial Proteins: Proteins encoded by the mitochondrial genome or proteins encoded by the nuclear genome that are imported to and resident in the MITOCHONDRIA.5'-Nucleotidase: A glycoprotein enzyme present in various organs and in many cells. The enzyme catalyzes the hydrolysis of a 5'-ribonucleotide to a ribonucleoside and orthophosphate in the presence of water. It is cation-dependent and exists in a membrane-bound and soluble form. EC 220.127.116.11.Suramin: A polyanionic compound with an unknown mechanism of action. It is used parenterally in the treatment of African trypanosomiasis and it has been used clinically with diethylcarbamazine to kill the adult Onchocerca. (From AMA Drug Evaluations Annual, 1992, p1643) It has also been shown to have potent antineoplastic properties.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Nucleotidases: A class of enzymes that catalyze the conversion of a nucleotide and water to a nucleoside and orthophosphate. EC 3.1.3.-.Sequence Homology, Nucleic Acid: The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.Glutamine: A non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from GLUTAMIC ACID and AMMONIA. It is the principal carrier of NITROGEN in the body and is an important energy source for many cells.Xanthines: Purine bases found in body tissues and fluids and in some plants.Nucleic Acid Conformation: The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.Adipose Tissue, Brown: A thermogenic form of adipose tissue composed of BROWN ADIPOCYTES. It is found in newborns of many species including humans, and in hibernating mammals. Brown fat is richly vascularized, innervated, and densely packed with MITOCHONDRIA which can generate heat directly from the stored lipids.Receptors, Purinergic P2: A class of cell surface receptors for PURINES that prefer ATP or ADP over ADENOSINE. P2 purinergic receptors are widespread in the periphery and in the central and peripheral nervous system.NAD: A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). (Dorland, 27th ed)Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Carcinoma, Ehrlich Tumor: A transplantable, poorly differentiated malignant tumor which appeared originally as a spontaneous breast carcinoma in a mouse. It grows in both solid and ascitic forms.Nucleotides, CyclicReceptors, Purinergic: Cell surface proteins that bind PURINES with high affinity and trigger intracellular changes which influence the behavior of cells. The best characterized classes of purinergic receptors in mammals are the P1 receptors, which prefer ADENOSINE, and the P2 receptors, which prefer ATP or ADP.Carbamyl Phosphate: The monoanhydride of carbamic acid with PHOSPHORIC ACID. It is an important intermediate metabolite and is synthesized enzymatically by CARBAMYL-PHOSPHATE SYNTHASE (AMMONIA) and CARBAMOYL-PHOSPHATE SYNTHASE (GLUTAMINE-HYDROLYZING).Phosphotransferases: A rather large group of enzymes comprising not only those transferring phosphate but also diphosphate, nucleotidyl residues, and others. These have also been subdivided according to the acceptor group. (From Enzyme Nomenclature, 1992) EC 2.7.Restriction Mapping: Use of restriction endonucleases to analyze and generate a physical map of genomes, genes, or other segments of DNA.Uric Acid: An oxidation product, via XANTHINE OXIDASE, of oxypurines such as XANTHINE and HYPOXANTHINE. It is the final oxidation product of purine catabolism in humans and primates, whereas in most other mammals URATE OXIDASE further oxidizes it to ALLANTOIN.Ion Channels: Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.Guanine Nucleotide Exchange Factors: Protein factors that promote the exchange of GTP for GDP bound to GTP-BINDING PROTEINS.Guanosine: A purine nucleoside that has guanine linked by its N9 nitrogen to the C1 carbon of ribose. It is a component of ribonucleic acid and its nucleotides play important roles in metabolism. (From Dorland, 28th ed)RNA: A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Mitochondria: Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed)Cell Line: Established cell cultures that have the potential to propagate indefinitely.Protein Binding: 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.Phosphates: Inorganic salts of phosphoric acid.Purinergic P2 Receptor Antagonists: Compounds that bind to and block the stimulation of PURINERGIC P2 RECEPTORS.Glycine: A non-essential amino acid. It is found primarily in gelatin and silk fibroin and used therapeutically as a nutrient. It is also a fast inhibitory neurotransmitter.Lyases: A class of enzymes that catalyze the cleavage of C-C, C-O, and C-N, and other bonds by other means than by hydrolysis or oxidation. (Enzyme Nomenclature, 1992) EC 4.Uncoupling Agents: Chemical agents that uncouple oxidation from phosphorylation in the metabolic cycle so that ATP synthesis does not occur. Included here are those IONOPHORES that disrupt electron transfer by short-circuiting the proton gradient across mitochondrial membranes.Nucleosides: Purine or pyrimidine bases attached to a ribose or deoxyribose. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Structure-Activity Relationship: The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.