Showing papers on "Tyrosine published in 1971"
TL;DR: The specificity of the assay has been demonstrated in experiments in which various factors that influence either tyrosine hydroxylase or aromatic l-amino acid decarboxylase activity were omitted, and the sensitivity of the method has been shown to be greater in the laboratory than tyrosin hydroxyase assays currently used.
454 citations
TL;DR: It is concluded that the previous reports that tyrosine hydroxylase is stimulated by Fe2+ can be explained by the known ability ofFe2+ to decompose H2O2.
381 citations
TL;DR: Treatment of newborn rats with 10 mug/g of nerve growth factor for 10 days enhanced not only the growth but also the differentiation of neuroblasts in superior cervical ganglia and the induction of trans-synaptic enzymes by increased activity of the sympathetic nervous system.
Abstract: Treatment of newborn rats with 10 μg/g of nerve growth factor for 10 days enhanced not only the growth but also the differentiation of neuroblasts in superior cervical ganglia. These morphological changes were accompanied by selective induction of tyrosine hydroxylase and dopamine β-hydroxylase (EC 1.14.2.1), whereas the total and specific activities of other enzymes involved in biosynthesis or metabolic degradation of norepinephrine rose only in proportion to the increase in volume of the sympathetic ganglia. There are remarkable similarities between this effect of nerve growth factor and the induction of trans-synaptic enzymes by increased activity of the sympathetic nervous system.
290 citations
TL;DR: It is proposed that ATP participates in an early phase of enzyme degradation, and was shown, in the case of tyrosine aminotransferase, to be rapidly reversible and exerted by a mechanism different from the inhibition of protein synthesis.
280 citations
TL;DR: While reduction of the disulfide bridges altered the yield of several proteins, it appeared to have no general effect on narrowing the range observed with a group of proteins, suggesting that either: (a) the amino acid sequence around a tryptophan in a disrupted peptide chain influences the yield, or (b) ‘residual’ three dimensional structure persists in reduced denatured proteins.
Abstract: — (1) By excitation at 295 nm tryptophan fluorescence from 17 proteins was examined free of contributions from tyrosine. The tryptophan quantum yields for native proteins were both higher and lower than that of the free amino acid and spanned a 5-fold range. No simple relationship was apparent between ‘exposure’ of tryptophyl side chains in proteins and the magnitude of the quantum yield or of the position of the emission maximum. (2) Denaturation of these proteins in 6 M guanidine hydrochloride considerably narrowed the range of values of yields (ca 0.1 to 0.17). While reduction of the disulfide bridges altered the yield of several proteins, it appeared to have no general effect on narrowing the range observed with a group of proteins, suggesting that either: (a) the amino acid sequence around a tryptophan in a disrupted peptide chain influences the yield, or (b) ‘residual’ three dimensional structure persists in reduced denatured proteins. (3) It was possible to demonstrate using both 280 and 295 nm excited spectra that tyrosine fluorescence, while weak, is generally present in proteins. These data also showed that transfer of the excited state from tyrosine to tryptophan is a common occurrence in native proteins and occurs with very high efficiency in a number of cases.
199 citations
TL;DR: A thrombin-like enzyme has been purified to homogeneity from the venom of Crotalus adamanteus (Eastern diamond-back rattlesnake) and is optimally active near pH 8 and is stable to neutral and alkaline pH; however, it loses activity upon exposure to acid pH.
156 citations
TL;DR: The results support the presence of a previously postulated interneuronal feedback mechanism in brain which can regulate dopamine synthesis and this may function at least in part through an effect on tyrosine hydroxylase activity.
101 citations
TL;DR: It was shown that iso-1-cytochrome c from one of the suppressed cy1 -9 strains contains a tyrosine at position 2, which corresponds to the site of the ochre codon in this mutant, and it is suggested that the gene product of the eight super-suppressors is tyosine transfer RNA.
97 citations
TL;DR: Evidence based on substrate specificity, inhibition by common substrates, inhibited by specific antibodies upon enzyme activity, and physical chemical properties indicate that the mitochondrial tyrosine aminotransferase is identical with mitochondrial aspartate aminotsferase.
85 citations
TL;DR: The use of these carboxyl-labeled amino acids simplifies the technical and theoretical complications that arise in measuring brain protein synthesis and allows studies impractical with many other radioactive amino acids.
83 citations
TL;DR: This study describes the daily rhythmic changes that occur in the concentrations of 12 amino acids in rat plasma, useful in assessing the significance of changes in plasma amino acid levels observed in rats several hours after particular experimental manipulations.
TL;DR: It is concluded that mutations causing the same phenotype as strains mutated in the tyrosine regulatory gene tyrR may be alleles of the tyrR gene and that synthesis of the enzymes listed above is controlled by this gene.
Abstract: Mutants of Escherichia coli K-12 were isolated in which the synthesis of the following, normally repressible enzymes of aromatic biosynthesis was constitutive: 3-deoxy-d-arabinoheptulosonic acid 7-phosphate (DAHP) synthetases (phe and tyr), chorismate mutase T-prephenate dehydrogenase, and transaminase A. In the wild type, DAHP synthetase (phe) was multivalently repressed by phenylalanine plus tryptophan, whereas DAHP synthetase (tyr), chorismate mutase T-prephenate dehydrogenase, and transaminase A were repressed by tyrosine. DAHP synthetase (tyr) and chorismate mutase T-prephenate dehydrogenase were also repressed by phenylalanine in high concentration (10(-3)m). Besides the constitutive synthesis of DAHP synthetase (phe), the mutants had the same phenotype as strains mutated in the tyrosine regulatory gene tyrR. The mutations causing this phenotype were cotransducible with trpA, trpE, cysB, and pyrF and mapped in the same region as tyrR at approximately 26 min on the chromosome. It is concluded that these mutations may be alleles of the tyrR gene and that synthesis of the enzymes listed above is controlled by this gene. Chorismate mutase P and prephenate dehydratase activities which are carried on a single protein were repressed by phenylalanine alone and were not controlled by tyrR. Formation of this protein is presumed to be controlled by a separate, unknown regulator gene. The heat-stable phenylalanine transaminase and two enzymes of the common aromatic pathway, 5-dehydroquinate synthetase and 5-dehydroquinase, were not repressible under the conditions studied and were not affected by tyrR. DAHP synthetase (trp) and tryptophan synthetase were repressed by tryptophan and have previously been shown to be under the control of the trpR regulatory gene. These enzymes also were unaffected by tyrR.
Journal Article•
TL;DR: The ability to produce significant anti-GAT 10 antibody, detected by an antigen-binding assay, was possessed by mice of H-2 a, H- 2 b,H-2 d, H -2 k histocompatibility alleles, which responded according to their H-1 type.
Abstract: Mice of various strains were immunized with a random terpolymer of glutamic acid 60 alanine 30 tyrosine 10 (GAT 10 ). The ability to produce significant anti-GAT 10 antibody, detected by an antigen-binding assay, was possessed by mice of H-2 a , H-2 b , H-2 d , H-2 k histocompatibility alleles. Mice with H-2 p and H-2 s alleles were non-responders. Congenic mice that differed only at the H-2 locus responded according to their H-2 type.
TL;DR: Genetic data show that the phenotypic expression of su(s)2 and the altered chromatographic pattern of tyrosine tRNA are recessive and that both map at the same position on the left tip of the X chromosome, indicating that the suppressor locus is not the locus for the primary structure of tyosine t RNA but that it may control an enzyme that modifies the tyrosin tRNA in some way.
TL;DR: It is concluded that there is a common catalytic site for both substrates and it is impossible to appreciably alter the ratio of the two activities during purification and isoelectric focusing.
Abstract: l-Phenylalanine ammonia-lyase (EC 4315) from maize is active with l-tyrosine and l-phenylalanine and exhibits atypical Michaelis-Menten kinetics with both substrates With phenylalanine as a substrate, the pH optimum is 87 and with tyrosine, 77 The estimated Km at high substrate concentrations is 027 mm for phenylalanine and 0029 mm for tyrosine However, the V(max) with phenylalanine is eight times higher than the V(max) with tyrosine when both are measured at pH 87, and 7 times higher when both are measured at their pH optima The following evidence leads us to the conclusion that there is a common catalytic site for both substrates: (a) It is impossible to appreciably alter the ratio of the two activities during purification and isoelectric focusing (b) The ratio of the products formed in mixed substrate experiments is in good agreement with the ratio predicted from the estimated Km values (c) NaBH(4) reduces both activities to the same degree and l-phenylalanine, l-tyrosine, cinnamate, and p-coumarate protect both activities against NaBH(4) reduction to the same degree In contrast, the enzyme isolated from potato, which does not act on l-tyrosine, is not protected against reduction by either l-tyrosine or p-coumarate However, both enzymes appear to have a dehydroalanine-containing prosthetic group
TL;DR: There is evidence to suggest that it exists in the mast cell not as a zymogen, but as the active enzyme, bound to heparin, which exhibits an exceptional affinity for Sephadex or Bio-Gel gels, and is strongly retarded in filtration on these in neutral 0.1 M salt solutions.
TL;DR: Spectrophotometric titration of cobrotoxin showed that one of the two tyrosyl groups was titrated freely with a normal apparent p K of 9.65, and the remaining one ionized with time only after irreversible conformational change had occurred at pH above 11.3.
TL;DR: Glycinin, the major soyabean globulin, is composed of subunits having molecular weights of about 22,300, and 37,200, and on the basis of amino acid analysis, the six submits of glycinin isolated by isoelectric focusing are all different.
Abstract: Glycinin, the major soyabean globulin, is composed of subunits having molecular weights of about 22,300, and 37,200. On the basis of amino acid analysis, the six submits of glycinin isolated by isoelectric focusing are all different. The ‘acidic’ subunits have higher content of glutamic acid and proline, whereas the ‘basic’ subunits are higher in the hydrophobic amino acids leucine, tyrosine, phenylalanine, valine and alanine.
TL;DR: Glycerol kinase of Escherichia coli was purified and crystallized by a gentle modified procedure and it was concluded that glycerol Kinase is an oligomeric protein composed of four identical subunits.
TL;DR: Disaggregation of brain polyribosomes preceded the increase in levels of phenylalanine in brain, and followed the same time course as depletion of tryptophan from brain.
Abstract: — Seven-day-old rats were injected intraperitoneally with l-phenylalanine (1 g/kg) and the time course of brain polyribosome disaggregation and changes in brain levels of phenylalanine, tryptophan and tyrosine were determined. Disaggregation of brain polyribosomes preceded the increase in levels of phenylalanine in brain, and followed the same time course as depletion of tryptophan from brain.
The effects of several metabolites of phenylalanine (which are formed in phenylketonuria) on protein synthesis in vitro was determined for brain and liver systems. None of the compounds tested was inhibitory at concentrations below 10 mM and in all cases hepatic protein synthesis was more sensitive to inhibition than was the corresponding system from brain.
Ribosomal dimers, formed in brain after injection of phenylalanine, were incapable of supporting high levels of protein synthesis in vitro, a finding that suggested that the inhibition of protein synthesis in vitro in cell-free systems of brain tissue after injection of phenylalanine into young rats was mediated by disaggregation of brain polyribosomes associated with tryptophan deficiency in brain.
TL;DR: Intraperitoneal injections of L-dopa decreased the concentrations of tryptophan, tyrosine and serotonin in rat brain in order to regulate the levels of serotonin and dopamine in the brain.
TL;DR: While tyrosine hydroxylase is normally rate limiting, dopamine-β-hydroxylation may become rate limiting when dopamine formation is markedly accelerated.
Abstract: Repeated intervals of immobilization previously have been found to cause elevation of levels of tyrosine hydroxylase in the adrenals of rats. In the present study it was found that the increased levels of enzymes result in enhanced synthesis of epinephrine-14C from tyrosine-14C but not from dopa-3H. During immobilization, conversion of tyrosine-14C to catecholamines is further increased and may exceed the capacity of even the elevated levels of dopa- mine-β-hydroxylase to convert dopamine to nor-epinephrine. Thus, while tyrosine hydroxylase is normally rate limiting, dopamine-β-hydroxylation may become rate limiting when dopamine formation is markedly accelerated. (Endocrinology 89: 46, 1971)
TL;DR: The similarity of the findings in the urine of a patient with hepatic soluble tyrosine aminotransferase deficiency and in tyrosyluric neonates suggests that delayed maturation of soluble tyruvic acid rather than p-hydroxyphenylpyruvate hydroxylase might be present in at least some of these infants.
Abstract: Extract: Metabolic studies on a patient having multiple congenital anomalies and defective hepatic soluble tyrosine aminotransferase activity are presented. The activities of hepatic mitochondrial tyrosine aminotransferase and soluble p-hydroxyphenylpyryvate hydroxylase were normal. When untreated, levels of tyrosine in plasma rose as high as 62 mg/100 ml. He had phenolic aciduri (3.1–4.9 mg/mg creatinine) with p-hydroxyphenylpyruvic acid (0.6-1.8 mg/mg creatinine), p-hydroxyphenylacetic acid (0.7–1.2 mg/mg creatinine), p-hydroxyphenyllactic acid (1.0–1.7 mg/mg creatinine), and N-acetyltyrosine (0.9–1.6 mg/mg creatinine). These metabolites were identified by gas chromatography-mass spectrometry. Excretion of p-tyramine was grossly elevated (17–44 μg/mg creatinine) and was not reduced by orally administered antibiotics. Oral tolerance tests showed rapid conversion of phenylpyruvic acid to phenylalanine and of phenylalanine to tyrosine. Speculation: The results described suggest the need to reexamine subcellular distribution of enzymes both in normal subkects and in patients with inborn errors of metabolism. When methods are developed to fractionate tyrosine aminotransferase, it may become apparent that there are several isozymes under individual genetic control. Accumulation of an intermediary metabolite should not be taken as conclusive evidence of a primary abnormality of its catabolism. The similarity of the findings in the urine of a patient with hepatic soluble tyrosine aminotransferase deficiency and in tyrosyluric neonates suggests that delayed maturation of soluble tyrosine aminotransferase rather than p-hydroxyphenylpyruvate hydroxylase might be present in at least some of these infants.
Journal Article•
TL;DR: Administration of 6-OH-dopamine daily for two days causes a nearly complete depletion of endogenous norepinephrine and a persistent, although not total, loss of activity of dopamine-β-hydroxylase from the heart.
Abstract: Administration of 6-OH-dopamine daily for two days causes a nearly complete depletion of endogenous norepinephrine and a persistent, although not total, loss of activity of dopamine-β-hydroxylase from the heart. In adrenal glands, 6-OH-dopamine administration increases the activity both of tyrosine hydroxylase and dopainine-β-hydroxylase without affecting catecholamine levels. In both normally innervated and decentralized sympathetic ganglia, administration of 6-OH-dopamine causes no change in tyrosine hydroxylase activity and a long-lasting 50% decrease in dopamine-β-hydroxylase activity. Pretreatment with 6-OH-dopamine prevents reserpine-induced. increases in the activity of these enzymes in ganglia. A similar effect is also produced by surgical section of the postganglionic axons of the superior cervical ganglion.
TL;DR: The low tissue concentrations of tetrahydrobiopterin, as well as the antagonism between the catecholamine feedback inhibition of tyrosine hydroxylase and the reduced cofactor concentrations, suggest that dihydropteridine reductase may play an important role in the regulation of catechlamine biosynthesis.
Abstract: The low tissue concentrations of tetrahydrobiopterin, as well as the antagonism between the catecholamine feedback inhibition of tyrosine hydroxylase and the reduced cofactor concentrations, suggest that dihydropteridine reductase may play an important role in the regulation of catecholamine biosynthesis.
The interaction of the different components involved in the hydroxylation of tyrosine was studied in vitro in a complex system composed of tyrosine hydroxylase, dihydropteridine reductase, and the different cofactors. This system has several important characteristics: (a) the rate of dihydroxyphenylalanine formation can be controlled by the concentration of dihydropteridine reductase; (b) low concentrations of catecholamines (2 × 10-5 M) can produce a marked inhibition of tyrosine hydroxylase activity; and (c) the catecholamine feedback-inhibition of tyrosine hydroxylase can be antagonized by increasing concentrations of dihydropteridine reductase.
The properties of the in vitro tyrosine hydroxylase-dihydropteridine reductase system suggest that dihydropteridine reductase may have an important role in vivo in the determination of the rates of dihydroxyphenylalanine formation and on the effectiveness of the catecholamine feedback-inhibition of tyrosine hydroxylase activity.
TL;DR: The yield of 3-nitrotyrosine from ovotransferrin after treatment with tetranitromethane was much smaller than the loss of tyrosine, and several unidentified compounds were also formed.
Abstract: 1. Tyrosine was treated with tetranitromethane. 2. Approx. 10% of the tyrosine was converted into 3-nitrotyrosine. 3. Three fluorescent compounds were also formed. They appear to be a dimer, trimer and tetramer in which tyrosine units are linked by biphenyl bonds. 4. The dimer and trimer have also been isolated from some proteins after treatment with tetranitromethane. 5. The yield of 3-nitrotyrosine from ovotransferrin after treatment with tetranitromethane was much smaller than the loss of tyrosine. 6. Several unidentified compounds were also formed by the reaction between tyrosine and tetranitromethane.
TL;DR: Main urinary bacterial metabolites of phenylalanine and tyrosine were determined by gas chromatography in controls and patients with cystic ubrosis of the pancreas, coeliac disease, intestinal resection and unclassified enteritis.
TL;DR: Those amino acids ordinarily considered nutritionally essential in the rat are taken up to a greater extent than nonessentials, particularly tyrosine, which may be related to the absence in brain of phenylalanine hydroxylase thus necessitating an external source.
Abstract: Summary14C-labeled amino acids were injected into rat common carotid artery mixed with 3H2O, with decapitation 15 sec later. The ratio of 14C to 3H in brain was compared with the same ratio in the injected solution allowing expression of brain uptake of amino acid as a percentage of 3H2O uptake. Eighteen amino acids showed a range of uptake between 2.24 and 54.5%. Those amino acids ordinarily considered nutritionally essential in the rat are taken up to a greater extent than nonessentials. The exception is tyrosine which is not nutritionally essential to the total organism because it is available from hydroxylation of phenylalanine. The large uptake of tyrosine by brain may be related to the absence in brain of phenylalanine hydroxylase thus necessitating an external source.