Phenylalanine: An essential aromatic amino acid that is a precursor of MELANIN; DOPAMINE; noradrenalin (NOREPINEPHRINE), and THYROXINE.Phenylalanine Hydroxylase: An enzyme of the oxidoreductase class that catalyzes the formation of L-TYROSINE, dihydrobiopterin, and water from L-PHENYLALANINE, tetrahydrobiopterin, and oxygen. Deficiency of this enzyme may cause PHENYLKETONURIAS and PHENYLKETONURIA, MATERNAL. EC Ammonia-Lyase: An enzyme that catalyzes the deamination of PHENYLALANINE to form trans-cinnamate and ammonia.Phenylketonurias: A group of autosomal recessive disorders marked by a deficiency of the hepatic enzyme PHENYLALANINE HYDROXYLASE or less frequently by reduced activity of DIHYDROPTERIDINE REDUCTASE (i.e., atypical phenylketonuria). Classical phenylketonuria is caused by a severe deficiency of phenylalanine hydroxylase and presents in infancy with developmental delay; SEIZURES; skin HYPOPIGMENTATION; ECZEMA; and demyelination in the central nervous system. (From Adams et al., Principles of Neurology, 6th ed, p952).Phenylpyruvic Acids: A group of compounds that are derivatives of phenylpyruvic acid which has the general formula C6H5CH2COCOOH, and is a metabolite of phenylalanine. (From Dorland, 28th ed)Tyrosine: A non-essential amino acid. In animals it is synthesized from PHENYLALANINE. It is also the precursor of EPINEPHRINE; THYROID HORMONES; and melanin.Amino Acids: Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.Ammonia-Lyases: Enzymes that catalyze the formation of a carbon-carbon double bond by the elimination of AMMONIA. EC 4.3.1.Prephenate Dehydratase: An enzyme that catalyzes the conversion of prephenate to phenylpyruvate with the elimination of water and carbon dioxide. In the enteric bacteria this enzyme also possesses chorismate mutase activity, thereby catalyzing the first two steps in the biosynthesis of phenylalanine. EC A natural product that has been considered as a growth factor for some insects.Pterins: Compounds based on 2-amino-4-hydroxypteridine.Kinetics: The rate dynamics in chemical or physical systems.Leucine: An essential branched-chain amino acid important for hemoglobin formation.Tryptophan: An essential amino acid that is necessary for normal growth in infants and for NITROGEN balance in adults. It is a precursor of INDOLE ALKALOIDS in plants. It is a precursor of SEROTONIN (hence its use as an antidepressant and sleep aid). It can be a precursor to NIACIN, albeit inefficiently, in mammals.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.Amino Acids, Aromatic: Amino acids containing an aromatic side chain.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.Phenylalanine-tRNA Ligase: An enzyme that activates phenylalanine with its specific transfer RNA. EC, Maternal: A condition occurring in untreated or partially treated females with PHENYLKETONURIA when they become pregnant. This may result in damages to the FETUS, including MICROCEPHALY; MENTAL RETARDATION; congenital heart disease; FETAL GROWTH RETARDATION; and CRANIOFACIAL ABNORMALITIES. (From Am J Med Genet 1997 Mar 3;69(1):89-95)Fenclonine: A selective and irreversible inhibitor of tryptophan hydroxylase, a rate-limiting enzyme in the biosynthesis of serotonin (5-HYDROXYTRYPTAMINE). Fenclonine acts pharmacologically to deplete endogenous levels of serotonin.p-Fluorophenylalanine: 3-(p-Fluorophenyl)-alanine.Chorismate Mutase: An isomerase that catalyzes the conversion of chorismic acid to prephenic acid. EC, Site-Directed: Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion.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.Amino Acids, Essential: Amino acids that are not synthesized by the human body in amounts sufficient to carry out physiological functions. They are obtained from dietary foodstuffs.Carbon Isotopes: 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.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Aspartame: Flavoring agent sweeter than sugar, metabolized as PHENYLALANINE and ASPARTIC ACID.Hydroxylation: Placing of a hydroxyl group on a compound in a position where one did not exist before. (Stedman, 26th ed)Pteridines: Compounds based on pyrazino[2,3-d]pyrimidine which is a pyrimidine fused to a pyrazine, containing four NITROGEN atoms.3-Deoxy-7-Phosphoheptulonate Synthase: An enzyme that catalyzes the formation of 7-phospho-2-keto-3-deoxy-D-arabinoheptonate from phosphoenolpyruvate and D-erythrose-4-phosphate. It is one of the first enzymes in the biosynthesis of TYROSINE and PHENYLALANINE. This enzyme was formerly listed as EC variabilis: A species of ANABAENA that can form SPORES called akinetes.Rhodotorula: A red yeast-like mitosporic fungal genus generally regarded as nonpathogenic. It is cultured from numerous sources in human patients.Nutritional Requirements: The amounts of various substances in food needed by an organism to sustain healthy life.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Hydro-Lyases: Enzymes that catalyze the breakage of a carbon-oxygen bond leading to unsaturated products via the removal of water. EC 4.2.1.Deuterium: Deuterium. The stable isotope of hydrogen. It has one neutron and one proton in the nucleus.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.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.Isoleucine: An essential branched-chain aliphatic amino acid found in many proteins. It is an isomer of LEUCINE. It is important in hemoglobin synthesis and regulation of blood sugar and energy levels.Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Phenylacetates: Derivatives of phenylacetic acid. Included under this heading are a variety of acid forms, salts, esters, and amides that contain the benzeneacetic acid structure. Note that this class of compounds should not be confused with derivatives of phenyl acetate, which contain the PHENOL ester of ACETIC ACID.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.Amino Acid Substitution: The naturally occurring or experimentally induced replacement of one or more AMINO ACIDS in a protein with another. If a functionally equivalent amino acid is substituted, the protein may retain wild-type activity. Substitution may also diminish, enhance, or eliminate protein function. Experimentally induced substitution is often used to study enzyme activities and binding site properties.Alanine: A non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases IMMUNITY, and provides energy for muscle tissue, BRAIN, and the CENTRAL NERVOUS SYSTEM.Muscle Proteins: The protein constituents of muscle, the major ones being ACTINS and MYOSINS. More than a dozen accessory proteins exist including TROPONIN; TROPOMYOSIN; and DYSTROPHIN.Protein Conformation: The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).RNA, Transfer, Phe: A transfer RNA which is specific for carrying phenylalanine to sites on the ribosomes in preparation for protein synthesis.Food, Formulated: Food and dietary formulations including elemental (chemically defined formula) diets, synthetic and semisynthetic diets, space diets, weight-reduction formulas, tube-feeding diets, complete liquid diets, and supplemental liquid and solid diets.Valine: A branched-chain essential amino acid that has stimulant activity. It promotes muscle growth and tissue repair. It is a precursor in the penicillin biosynthetic pathway.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.Leucine Dehydrogenase: An octameric enzyme belonging to the superfamily of amino acid dehydrogenases. Leucine dehydrogenase catalyzes the reversible oxidative deamination of L-LEUCINE, to 4-methyl-2-oxopentanoate (2-ketoisocaproate) and AMMONIA, with the corresponding reduction of the cofactor NAD+.Chromobacterium: A genus of gram-negative, facultatively anaerobic, rod-shaped bacteria occurring in soil and water. Its organisms are generally nonpathogenic, but some species do cause infections of mammals, including humans.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.Aldehyde-Lyases: Enzymes that catalyze a reverse aldol condensation. A molecule containing a hydroxyl group and a carbonyl group is cleaved at a C-C bond to produce two smaller molecules (ALDEHYDES or KETONES). EC 4.1.2.Lysine: An essential amino acid. It is often added to animal feed.Oxidation-Reduction: 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).Recombinant Proteins: Proteins prepared by recombinant DNA technology.Methionine: A sulfur-containing essential L-amino acid that is important in many body functions.Protein Biosynthesis: The biosynthesis of PEPTIDES and PROTEINS on RIBOSOMES, directed by MESSENGER RNA, via TRANSFER RNA that is charged with standard proteinogenic AMINO ACIDS.Dietary Proteins: Proteins obtained from foods. They are the main source of the ESSENTIAL AMINO ACIDS.RNA, Transfer: The small RNA molecules, 73-80 nucleotides long, that function during translation (TRANSLATION, GENETIC) to align AMINO ACIDS at the RIBOSOMES in a sequence determined by the mRNA (RNA, MESSENGER). There are about 30 different transfer RNAs. Each recognizes a specific CODON set on the mRNA through its own ANTICODON and as aminoacyl tRNAs (RNA, TRANSFER, AMINO ACYL), each carries a specific amino acid to the ribosome to add to the elongating peptide chains.Shikimic Acid: A tri-hydroxy cyclohexene carboxylic acid important in biosynthesis of so many compounds that the shikimate pathway is named after it.RNA, Transfer, Amino Acyl: Intermediates in protein biosynthesis. The compounds are formed from amino acids, ATP and transfer RNA, a reaction catalyzed by aminoacyl tRNA synthetase. They are key compounds in the genetic translation process.TetrosesPhosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.Amino Acids, Branched-Chain: Amino acids which have a branched carbon chain.Hydrogen-Ion Concentration: 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)Dihydropteridine Reductase: An enzyme that catalyzes the reduction of 6,7-dihydropteridine to 5,6,7,8-tetrahydropteridine in the presence of NADP+. Defects in the enzyme are a cause of PHENYLKETONURIA II. Formerly listed as EC A nonmetallic, diatomic gas that is a trace element and member of the halogen family. It is used in dentistry as flouride (FLUORIDES) to prevent dental caries.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.Protein Structure, Tertiary: 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.Catalysis: The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.Mitosporic Fungi: A large and heterogenous group of fungi whose common characteristic is the absence of a sexual state. Many of the pathogenic fungi in humans belong to this group.Protein HydrolysatesCloning, 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.CinnamatesPoint Mutation: A mutation caused by the substitution of one nucleotide for another. This results in the DNA molecule having a change in a single base pair.Transaminases: A subclass of enzymes of the transferase class that catalyze the transfer of an amino group from a donor (generally an amino acid) to an acceptor (generally a 2-keto acid). Most of these enzymes are pyridoxyl phosphate proteins. (Dorland, 28th ed) EC 2.6.1.Amino Acids, Neutral: Amino acids with uncharged R groups or side chains.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Spectrophotometry, Ultraviolet: Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Enzyme Activation: Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.Tyrosine Transaminase: An enzyme that catalyzes the conversion of L-TYROSINE and 2-oxoglutarate to 4-hydroxyphenylpyruvate and L-GLUTAMATE. It is a pyridoxal-phosphate protein. L-PHENYLALANINE is hydroxylated to L-tyrosine. The mitochondrial enzyme may be identical with ASPARTATE AMINOTRANSFERASES (EC Deficiency of this enzyme may cause type II Tyrosinemia (see TYROSINEMIAS). EC 1,2-Dioxygenase: A mononuclear Fe(II)-dependent oxygenase, this enzyme catalyzes the conversion of homogentisate to 4-maleylacetoacetate, the third step in the pathway for the catabolism of TYROSINE. Deficiency in the enzyme causes ALKAPTONURIA, an autosomal recessive disorder, characterized by homogentisic aciduria, OCHRONOSIS and ARTHRITIS. This enzyme was formerly characterized as EC and EC A plant genus of the family APIACEAE used for flavoring food.Dipeptides: Peptides composed of two amino acid units.Amino Acyl-tRNA Synthetases: A subclass of enzymes that aminoacylate AMINO ACID-SPECIFIC TRANSFER RNA with their corresponding AMINO ACIDS.Electrophoresis, Polyacrylamide Gel: Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Cyclohexanecarboxylic AcidsMagnetic Resonance Spectroscopy: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Stereoisomerism: 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)Molecular Weight: The sum of the weight of all the atoms in a molecule.Chromatography, High Pressure Liquid: Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.Radioactive Tracers: Radioactive substances added in minute amounts to the reacting elements or compounds in a chemical process and traced through the process by appropriate detection methods, e.g., Geiger counter. Compounds containing tracers are often said to be tagged or labeled. (Hawley's Condensed Chemical Dictionary, 12th ed)Tryptophan Hydroxylase: An enzyme that catalyzes the hydroxylation of TRYPTOPHAN to 5-HYDROXYTRYPTOPHAN in the presence of NADPH and molecular oxygen. It is important in the biosynthesis of SEROTONIN.Sequence Alignment: 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.

Prior protein intake may affect phenylalanine kinetics measured in healthy adult volunteers consuming 1 g protein. kg-1. d-1. (1/4047)

Study of the amino acid metabolism of vulnerable groups, such as pregnant women, children and patients, is needed. Our existing protocol is preceded by 2 d of adaptation to a low 13C formula diet at a protein intake of 1 g. kg-1. d-1 to minimize variations in breath 13CO2 enrichment and protein metabolism. To expand on our potential study populations, a less invasive protocol needs to be developed. We have already established that a stable background 13CO2 enrichment can be achieved on the study day without prior adaptation to the low 13C formula. Therefore, this study investigates phenylalanine kinetics in response to variations in prior protein intake. Healthy adult subjects were each fed nutritionally adequate mixed diets containing 0.8, 1.4 and 2.0 g protein. kg-1. d-1 for 2 d. On d 3, subjects consumed an amino acid-based formula diet containing the equivalent of 1 g protein. kg-1. d-1 hourly for 10 h and primed hourly oral doses of L-[1-13C]phenylalanine for the final 6 h. Phenylalanine kinetics were calculated from plasma-free phenylalanine enrichment and breath 13CO2 excretion. A significant quadratic response of prior protein intake on phenylalanine flux (P = 0.012) and oxidation (P = 0.009) was identified, such that both variables were lower following adaptation to a protein intake of 1.4 g. kg-1. d-1. We conclude that variations in protein intake, between 0.8 and 2.0 g. kg-1. d-1, prior to the study day may affect amino acid kinetics and; therefore, it is prudent to continue to control protein intake prior to an amino acid kinetics study.  (+info)

Phe161 and Arg166 variants of p-hydroxybenzoate hydroxylase. Implications for NADPH recognition and structural stability. (2/4047)

Phe161 and Arg166 of p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens belong to a newly discovered sequence motif in flavoprotein hydroxylases with a putative dual function in FAD and NADPH binding [1]. To study their role in more detail, Phe161 and Arg166 were selectively changed by site-directed mutagenesis. F161A and F161G are catalytically competent enzymes having a rather poor affinity for NADPH. The catalytic properties of R166K are similar to those of the native enzyme. R166S and R166E show impaired NADPH binding and R166E has lost the ability to bind FAD. The crystal structure of substrate complexed F161A at 2.2 A is indistinguishable from the native enzyme, except for small changes at the site of mutation. The crystal structure of substrate complexed R166S at 2.0 A revealed that Arg166 is important for providing an intimate contact between the FAD binding domain and a long excursion of the substrate binding domain. It is proposed that this interaction is essential for structural stability and for the recognition of the pyrophosphate moiety of NADPH.  (+info)

The accessibility of iron at the active site of recombinant human phenylalanine hydroxylase to water as studied by 1H NMR paramagnetic relaxation. Effect of L-Phe and comparison with the rat enzyme. (3/4047)

The high-spin (S = 5/2) Fe(III) ion at the active site of recombinant human phenylalanine hydroxylase (PAH) has a paramagnetic effect on the longitudinal relaxation rate of water protons. This effect is proportional to the concentration of enzyme, with a paramagnetic molar-relaxivity value at 400 MHz and 25 degrees C of 1. 3 (+/- 0.03) x 10(3) s-1 M-1. The value of the Arrhenius activation energy (Ea) for the relaxation rate was -14.4 +/- 1.1 kJ/mol for the resting enzyme, indicating a fast exchange of water protons in the paramagnetic environment. The frequency dependence of the relaxation rate also supported this hypothesis. Thus, the recombinant human PAH appears to have a more solvent-accessible catalytic iron than the rat enzyme, in which the water coordinated to the metal is slowly exchanging with the solvent. These findings may be related to the level of basal activity before activation for these enzymes, which is higher for human than for rat PAH. In the presence of saturating (5 mM) concentrations of the substrate L-Phe, the paramagnetic molar relaxivity for human PAH decreased to 0.72 (+/- 0.05) x 10(3) s-1 M-1 with no significant change in the Ea. Effective correlation times (tauC) of 1.8 (+/- 0.3) x 10(-10) and 1.25 (+/- 0.2) x 10(-10) s-1 were calculated for the enzyme and the enzyme-substrate complex, respectively, and most likely represent the electron spin relaxation rate (tauS) for Fe(III) in each case. Together with the paramagnetic molar-relaxivity values, the tauC values were used to estimate Fe(III)-water distances. It seems that at least one of the three water molecules coordinated to the iron in the resting rat and human enzymes is displaced from coordination on the binding of L-Phe at the active site.  (+info)

A different approach to treatment of phenylketonuria: phenylalanine degradation with recombinant phenylalanine ammonia lyase. (4/4047)

Phenylketonuria (PKU), with its associated hyperphenylalaninemia (HPA) and mental retardation, is a classic genetic disease and the first to have an identified chemical cause of impaired cognitive development. Treatment from birth with a low phenylalanine diet largely prevents the deviant cognitive phenotype by ameliorating HPA and is recognized as one of the first effective treatments of a genetic disease. However, compliance with dietary treatment is difficult and when it is for life, as now recommended by an internationally used set of guidelines, is probably unrealistic. Herein we describe experiments on a mouse model using another modality for treatment of PKU compatible with better compliance using ancillary phenylalanine ammonia lyase (PAL, EC to degrade phenylalanine, the harmful nutrient in PKU; in this treatment, PAL acts as a substitute for the enzyme phenylalanine monooxygenase (EC, which is deficient in PKU. PAL, a robust enzyme without need for a cofactor, converts phenylalanine to trans-cinnamic acid, a harmless metabolite. We describe (i) an efficient recombinant approach to produce PAL enzyme, (ii) testing of PAL in orthologous N-ethyl-N'-nitrosourea (ENU) mutant mouse strains with HPA, and (iii) proofs of principle (PAL reduces HPA)-both pharmacologic (with a clear dose-response effect vs. HPA after PAL injection) and physiologic (protected enteral PAL is significantly effective vs. HPA). These findings open another way to facilitate treatment of this classic genetic disease.  (+info)

Rho family small G proteins play critical roles in mechanical stress-induced hypertrophic responses in cardiac myocytes. (5/4047)

-Mechanical stress induces a variety of hypertrophic responses, such as activation of protein kinases, reprogramming of gene expression, and an increase in protein synthesis. In the present study, to elucidate how mechanical stress induces such events, we examined the role of Rho family small GTP-binding proteins (G proteins) in mechanical stress-induced cardiac hypertrophy. Treatment of neonatal rat cardiomyocytes with the C3 exoenzyme, which abrogates Rho functions, suppressed stretch-induced activation of extracellular signal-regulated protein kinases (ERKs). Overexpression of the Rho GDP dissociation inhibitor (Rho-GDI), dominant-negative mutants of RhoA (DNRhoA), or DNRac1 significantly inhibited stretch-induced activation of transfected ERK2. Overexpression of constitutively active mutants of RhoA slightly activated ERK2 in cardiac myocytes. Overexpression of C-terminal Src kinase, which inhibits functions of the Src family of tyrosine kinases, or overexpression of DNRas had no effect on stretch-induced activation of transfected ERK2. The promoter activity of skeletal alpha-actin and c-fos genes was increased by stretch, and these increases were completely inhibited by either cotransfection of Rho-GDI or pretreatment with C3 exoenzyme. Mechanical stretch increased phenylalanine incorporation into cardiac myocytes by approximately 1.5-fold compared with control, and this increase was also significantly suppressed by pretreatment with C3 exoenzyme. Overexpression of Rho-GDI or DNRhoA did not affect angiotensin II-induced activation of ERK. ERKs were activated by culture media conditioned by stretch of cardiomyocytes without any treatment, but not of cardiomyocytes with pretreatment by C3 exoenzyme. These results suggest that the Rho family of small G proteins plays critical roles in mechanical stress-induced hypertrophic responses.  (+info)

Role of aromaticity of agonist switches of angiotensin II in the activation of the AT1 receptor. (6/4047)

We have shown previously that the octapeptide angiotensin II (Ang II) activates the AT1 receptor through an induced-fit mechanism (Noda, K., Feng, Y. H., Liu, X. P., Saad, Y., Husain, A., and Karnik, S. S. (1996) Biochemistry 35, 16435-16442). In this activation process, interactions between Tyr4 and Phe8 of Ang II with Asn111 and His256 of the AT1 receptor, respectively, are essential for agonism. Here we show that aromaticity, primarily, and size, secondarily, of the Tyr4 side chain are important in activating the receptor. Activation analysis of AT1 receptor position 111 mutants by various Ang II position 4 analogues suggests that an amino-aromatic bonding interaction operates between the residue Asn111 of the AT1 receptor and Tyr4 of Ang II. Degree and potency of AT1 receptor activation by Ang II can be recreated by a reciprocal exchange of aromatic and amide groups between positions 4 and 111 of Ang II and the AT1 receptor, respectively. In several other bonding combinations, set up between Ang II position 4 analogues and receptor mutants, the gain of affinity is not accompanied by gain of function. Activation analysis of position 256 receptor mutants by Ang II position 8 analogues suggests that aromaticity of Phe8 and His256 side chains is crucial for receptor activation; however, a stacked rather than an amino-aromatic interaction appears to operate at this switch locus. Interaction between these residues, unlike the Tyr4:Asn111 interaction, plays an insignificant role in ligand docking.  (+info)

Identification of determinants in E2 ubiquitin-conjugating enzymes required for hect E3 ubiquitin-protein ligase interaction. (7/4047)

Members of the hect domain protein family are characterized by sequence similarity of their C-terminal regions to the C terminus of E6-AP, an E3 ubiquitin-protein ligase. An essential intermediate step in E6-AP-dependent ubiquitination is the formation of a thioester complex between E6-AP and ubiquitin in the presence of distinct E2 ubiquitin-conjugating enzymes including human UbcH5, a member of the UBC4/UBC5 subfamily of E2s. Similarly, several hect domain proteins, including Saccharomyces cerevisiae RSP5, form ubiquitin thioester complexes, indicating that hect domain proteins in general have E3 activity. We show here, by the use of chimeric E2s generated between UbcH5 and other E2s, that a region of UbcH5 encompassing the catalytic site cysteine residue is critical for its ability to interact with E6-AP and RSP5. Of particular importance is a phenylalanine residue at position 62 of UbcH5 that is conserved among the members of the UBC4/UBC5 subfamily but is not present in any of the other known E2s, whereas the N-terminal 60 amino acids do not contribute significantly to the specificity of these interactions. The conservation of this phenylalanine residue throughout evolution underlines the importance of the ability to interact with hect domain proteins for the cellular function of UBC4/UBC5 subfamily members.  (+info)

Mechanism of the cleavage specificity of Alzheimer's disease gamma-secretase identified by phenylalanine-scanning mutagenesis of the transmembrane domain of the amyloid precursor protein. (8/4047)

Proteolytic processing of the amyloid precursor protein by beta-secretase yields A4CT (C99), which is cleaved further by the as yet unknown gamma-secretase, yielding the beta-amyloid (Abeta) peptide with 40 (Abeta40) or 42 residues (Abeta42). Because the position of gamma-secretase cleavage is crucial for the pathogenesis of Alzheimer's disease, we individually replaced all membrane-domain residues of A4CT outside the Abeta domain with phenylalanine, stably transfected the constructs in COS7 cells, and determined the effect of these mutations on the cleavage specificity of gamma-secretase (Abeta42/Abeta40 ratio). Compared with wild-type A4CT, mutations at Val-44, Ile-47, and Val-50 led to decreased Abeta42/Abeta40 ratios, whereas mutations at Thr-43, Ile-45, Val-46, Leu-49, and Met-51 led to increased Abeta42/Abeta40 ratios. A massive effect was observed for I45F (34-fold increase) making this construct important for the generation of animal models for Alzheimer's disease. Unlike the other mutations, A4CT-V44F was processed mainly to Abeta38, as determined by mass spectrometry. Our data provide a detailed model for the active site of gamma-secretase: gamma-secretase interacts with A4CT by binding to one side of the alpha-helical transmembrane domain of A4CT. Mutations in the transmembrane domain of A4CT interfere with the interaction between gamma-secretase and A4CT and, thus, alter the cleavage specificity of gamma-secretase.  (+info)

  • Phenylalanine belongs to a particular group of amino acids known as essential amino acids, which basically means that they are needed by the body to carry our its everyday functions, but that the body itself cannot manufacture them, so they must be obtained by dietary means. (
  • D-phenylalanine is a synthetic form of phenylalanine that mirrors its natural cousin, and DL-phenylalanine therefore is a combination of these two amino acids. (
  • The Main Products Include: Alanine Series , Phenylalanine Series , Aspartic Acid Series , Glutamic Acid Series And D-Amino Acids , For A Characteristic To Point Out , DL-Amino Acids Synthesis Technology And High Optical Purity Amino Acids Production Technology. (
  • a "phenylketonuric" compound associated to PKU or phenylketonuria disease, a group of symptoms associated to mental retardation and cognitive impairments in the brain, where excess phenylalanine is converted to a ketone in the CNS periphery (Central Nervous System). (
  • Phenylalanine supplements should not be taken by individuals with phenylketonuria (PKU), children, pregnant or lactating women, people with high blood pressure, and anyone taking anti-psychotic medications or MAO inhibitors. (
  • Supplements can contain either form or a mixture of their equal amounts, known as DLPA (DL-phenylalanine) . (
  • Sometimes children are born without the ability to manufacture an enzyme crucial to the metabolizing of phenylalanine, a condition known as PKU . (
  • D-phenylalanine is reported to inhibit an enzyme that degrades enkephalins, which are naturally occurring substances in the body that belong to the class of compounds known as "endorphins. (
  • Phenylalanine has potential health benefits for the skin and brain, but some people should avoid it by all means. (
  • Phenylalanine plays a key role in the biosynthesis of other amino acids and some neurotransmitters. (
  • Phenylalanine ammonialyase (PAL) catalyzes the first step in the biosynthesis of phenylpropanoids, and is usually encoded by a multi-gene family. (
  • Identification and characterization of CYP79D16 and CYP71AN24 catalyzing the first and second steps in L-phenylalanine-derived cyanogenic glycoside biosynthesis in the Japanese apricot, Prunus mume Sieb. (
  • Valine and phenylalanine as precursors in the biosynthesis of alkamides in Acmella radicans. (
  • Alkamides were isolated from young A. radicans plants and analyzed by gas chromatography-mass spectrometry (GC-MS). Additionally, in cell free in vitro experiments based on isobutyl and phenylethylamide biosynthesis, using a colorimetric assay and GC-MS, valine and phenylalanine decarboxylase activities were assayed in the soluble extract of A. radicans leaves. (
  • The dietary supplement from Source Naturals‚ DL-Phenylalanine 750 mg 60 Tablets‚ may possibly help in the support of an alert state of mind. (
  • The test detects abnormally high levels of an amino acid called phenylalanine. (
  • This test is done to screen infants for PKU, a fairly rare condition that occurs when the body lacks a substance needed to breakdown the amino acid phenylalanine. (
  • Phenylalanine (Phe) is an α-amino acid with the formula C 9H 11NO 2. (
  • Phenylalanine is an amino acid, a "building block" of protein. (
  • D-phenylalanine is not an essential amino acid. (
  • L-phenylalanine is an essential amino acid. (
  • Phenylalanine, a naturally occurring amino acid, is not present in chewing gum products on its own. (
  • A process is disclosed for preparing phenylalanine which comprises contacting phenylpyruvic acid or phenylpyruvate with immobilized whole cells having transaminase activity in the presence of an amine donor. (
  • 1. A process for preparing phenylalanine which comprises preparing an aqueous reaction mixture consisting essentially of phenylpyruvic acid or phenylpyruvate, pyridoxal -5-phosphate as a cofactor and an amine donor selected from the group consisting of L-glutamic acid and L-aspartic acid, and contacting said reaction mixture with cells immobilized with a polyazetidine polymer, the cells having transaminase activity to obtain said phenylalanine in high yield. (
  • 13. A composition suitable for use in converting phenylpyruvic acid or phenylpyruvate to phenylalanine comprising immobilized cells having transaminase activity, said cells being immobilized with a polyazetidine polymer. (
  • Phenylalanine is an essential amino acid that is also one of the aromatic amino acids that exhibit ultraviolet radiation absorption properties with a large extinction coefficient. (
  • Your body is unable to produce enough L-phenylalanine on its own, so it's considered an essential amino acid that must be obtained through your diet ( 4 ). (
  • This amino acid is produced directly from phenylalanine. (
  • Phenylalanine is an essential amino acid that the body can not synthesize and therefore must be provided by the diet. (
  • Phenylalanine is an essential amino acid that must be supplemented through diet. (
  • D-phenylalanine is a synthetic form of this amino acid created in a laboratory. (
  • and DL-phenylalanine, a combination of the first two forms of this amino acid. (
  • It is made by our bodies from phenylalanine, which is an essential amino acid and must be consumed daily. (
  • One reason that PKU is so devastating is that a high level of Phenylalanine (Phe), which is a large neutral amino acid (LNAA), stops other LNAAs, which are needed for proper brain development, getting into the brain. (
  • Exposure to the amino acid L-phenylalanine increased release of CCK by 135%, 180%, and 251% of control levels after 15-min treatments with 5, 20, and 50 mM phenylalanine, respectively. (
  • PAL, a robust enzyme without need for a cofactor, converts phenylalanine to trans-cinnamic acid, a harmless metabolite. (
  • The amino acid phenylalanine (Phe) is a critical metabolic node that plays an essential role in the interconnection between primary and secondary metabolism in plants. (
  • One such dietary amino acid, phenylalanine (Phe), is a critical metabolic node that plays an essential role in the interconnection between the primary and secondary metabolism of plants. (
  • Taking the amino acid phenylalanine as a pre-workout supplement may stimulate whole body fat oxidation, known colloquially as 'burning fat,' according to a new study. (
  • The researchers wrote that effects of a single amino acid combined with exercise on fat oxidation is still unclear, thus the research was to investigate hormone secretion induced by phenylalanine and exercise. (
  • The aim of this research is to investigate the inhibitive effect of amino acid such as DL-phenylalanine. (
  • C9H11NO2 amino acid Phenylalanine molecule isolated on white. (
  • Phenylalanine - an essential amino acid- is readily available in most food sources, particularly high in meats and milk products, with lower levels found in oats and wheat germ. (
  • Because L-phenylalanine is an essential amino acid, it is not synthesized in the human body and must be supplied by dietary intake or supplementation. (
  • Liu, J. and Liu, X. (2011), Nanoparticles prepared by blending of carboxylic acid terminated poly(ε-caprolactone) and L -phenylalanine substituted dextran. (
  • Limited clinical research performed in the 1970s and 1980s suggests L-phenylalanine or DL-phenylalanine might be useful for depression. (
  • Taking D-phenylalanine does not appear to improve symptoms of depression. (
  • Phenylalanine has been studied as a treatment for several medical conditions, including skin disorders, depression and pain ( 3 ). (
  • Since phenylalanine is used to make these molecules in your body, it has been studied as a potential treatment for certain conditions, including depression ( 9 ). (
  • Thus, food intake with phenylalanine may help reduce the symptoms of depression and Alzheimer's . (
  • One animal study suggests that D-phenylalanine may improve rigidity, walking disabilities, speech difficulties, and depression associated with Parkinson disease. (
  • Studies suggest that phenylalanine may be helpful as part of a comprehensive therapy for depression, most of the studies were done in the 1970s and 1980s and were not rigorously tested. (
  • More research is needed to tell whether phenylalanine has any real effect on depression. (
  • According to Integrative Medical Arts Group, DL-phenylalanine and phenylethylamine may improve symptoms of both Parkinson's and the depression that occurs with the disease. (
  • While they both worked equally well at reducing the symptoms of depression, the D-phenylalanine showed marked improvements after just 15 days, rather than several weeks for the imipramine. (
  • DL-Phenylalanine is used to relieve cases of minor depression and other mood issues as well as and physical discomforts and pain. (
  • Phenylalanine can affect depression via three separate pathways. (
  • Therapeutic doses of phenylalanine may have useful roles in the management of blood pressure disorders and the control of certain forms of depression. (
  • Depression is a common use for L-phenylalanine or DL-phenylalanine. (
  • L-phenylalanine has been found to improve mood in people who have major depression. (
  • DL-phenylalanine and D-phenylalanine have also been studied for depression, although the results are unclear. (
  • Pregnant women with hyperphenylalaninemia may show similar symptoms of the disorder (high levels of phenylalanine in blood) but these indicators will usually disappear at the end of gestation. (
  • You can take phenylalanine as a capsule, powder, or tablet. (
  • Researchers found that participants who consumed 3g of phenylalanine in a capsule thirty minutes before exercising exhibited increased concentrations of plasma glycerol and the hormone glucagon-both relevant in the process of converting fat into usable energy. (
  • The capsule of phenylalanine came from ingredient manufacturer Kyowa Hakko, which is owned by the beverage giant Kirin Holdings. (
  • At the recommended dosage‚ each 90-capsule bottle of Pure Encapsulations' dl-Phenylalanine should last for about 15 to 22 days. (
  • Douglas Labs L-Phenylalanine 90 caps supplies 500 mg of pure L-Phenylalanine in each capsule. (
  • DL-Phenylalanine (Free Form) (providing D-Phenylalanine and L-Phenylalanine), Vegetable Capsule Shell: hydroxypropylmethyl cellulose, Anti-caking Agents: (vegetable magnesium stearate, silicon dioxide), Bulking Agent: hydroxypropyl cellulose. (
  • The first description of phenylalanine was made in 1879, when Schulze and Barbieri identified a compound with the empirical formula, C9H11NO2, in yellow lupine (Lupinus luteus) seedlings. (
  • Present treatment relies on the observation that a (semisynthetic) diet low in phenylalanine ( 3 - 5 ) will prevent HPA and thus the disease. (
  • Treatment includes the early introduction of a diet low in phenylalanine. (
  • Preliminary studies suggest that L-phenylalanine (oral and topical) strengthens the effect of UVA radiation for people with vitiligo. (
  • Studies suggest that L-phenylalanine in combination with exposure to ultraviolet A (UVA) light or sunlight may help treat vitiligo, a condition in which there is a loss of skin pigment. (
  • Patients who are heterozygous for a GTPCH mutation, despite their normal blood phenylalanine levels on routine screening, can be shown to have abnormal phenylalanine metabolism if stressed by administration of an oral phenylalanine load (100 mg/kg). (
  • Pregnant women with PKU must control their blood phenylalanine levels even if the fetus is heterozygous for the defective gene because the fetus could be adversely affected due to hepatic immaturity. (
  • Some research suggests that patients with ADHD have lower levels of amino acids such as phenylalanine, so there was hope that providing phenylalanine might treat ADHD. (
  • Early research suggests that taking D-phenylalanine by mouth might enhance acupuncture anesthesia while having a tooth pulled. (
  • Early research suggests that taking a combination of D-phenylalanine, L-glutamine, and L-5-hydroxytryptophan for 40 days can improve some symptoms of alcohol withdrawal. (
  • Early research suggests that using Cari Loder's regiment, which includes L-phenylalanine, lofepramine, and intramuscular vitamin B12 for 24 weeks, does not improve disability in people with multiple sclerosis. (
  • Limited research suggests taking one form of phenylalanine (D-phenylalanine) might decrease symptoms of Parkinson's disease. (
  • Research database Health Notes Online suggests the use of L-phenylalanine while patients are undergoing ultraviolet radiation therapy. (
  • Some research suggests that tardive dyskinesia patients may process phenylalanine abnormally. (
  • Certain researchers suggests the possibility that D-Phenylalanine may inhibit the action of enzymes that break down endorphins (the feel-good hormone) and enkephalins. (
  • The Cari Loder regime is a proposed method of treatment for multiple sclerosis (MS) that includes L-phenylalanine, lofepramine, and vitamin B12 injected into the vein. (
  • The MP Diagnostics ImmuChem Phenylalanine ELISA Kit is designed for the quantitative determination of phenylalanine in neonatal blood spots. (
  • Certain research indicates that the ingredients formulated into DL-Phenylalanine may be potentially successful at boosting endorphins. (
  • Food with a high phenylalanine content are meat products or animal-based products in general such as poultry, eggs and milk. (
  • The test paper is taken to the laboratory, where it is mixed with a type of bacteria that needs phenylalanine to grow. (
  • PAH is needed to process phenylalanine, although other, non-PAH gene mutations can also cause PKU. (
  • People have reported that their mood improved when they took phenylalanine. (
  • Other studies suggest that elevated phenylalanine concentrations are linked to mood swings. (
  • d-Phenylalanine and l-Phenylalanine work in combination to help you maintain a positive mood. (
  • L-phenylalanine can also be converted (through a separate pathway) to phenylethylamine, a substance that occurs naturally in the brain and appears to elevate mood. (
  • In enzymology, a phenylalanine adenylyltransferase (EC is an enzyme that catalyzes the chemical reaction ATP + L-phenylalanine ⇌ {\displaystyle \rightleftharpoons } diphosphate + N-adenylyl-L-phenylalanine Thus, the two substrates of this enzyme are ATP and L-phenylalanine, whereas its two products are diphosphate and N-adenylyl-L-phenylalanine. (