Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: DrugBank:EXPT03141 (L-tyrosine)
 2,375 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Maximal levels of L-henylalanine ammonia-lyase activity were observed when the mycelial felts of Rhizoctonia solani were grown for 4.5 days on Byrde synthetic medium containing 3.5% glucose and 0.3% L-phenylalanine, Differential centrifugation studies have indicated that the enzyme is localized in the soluble fraction. The time course of induction of L-phenylalanine ammonia-lyase activity by L-phenylalanine showed a lag period of 1 to 1.5 h and reached a maximum around 4 to 6 h after the addition of the inducer to the medium. L-Phenylalanine, L-tyrosine, and L-tryptophan were nearly equally efficient inducers of the enzyme. D-Phenylalanine was as efficient as the L-isomer, whereas D-tyrosine was a poor inducer. Light, gibberellic acid, indole 3-acetic acid, and kinetin had no effect on the induction of L-phenylalanine ammonia-lyase activity. Cycloheximide did not inhibit the uptake of amino acids by the mycelia but completely blocked the incorporation of radioactive amino acids into soluble proteins and the development of L-phenylalanine ammonia-lyase activity. Actinomycin D inhibited both the incorporation of 32P into ribonucleic acid and the enzyme activity. Conclusive evidence for de novo synthesis of L-phenylalanine ammonia-lyase was obtained by the incorporation of radioactive amino acids into the enzyme. Electrophoretic analysis of the purified preparation showed a single protein band that coincided with radioactivity and L-phenylalanine ammonia-lyase activity. Glucose and intermediates of the tricarboxylic acid cycle, like citric acid, alpha-ketoglutaric acid, and succinic acid, and the metabolites of L-phenylalanine, like o-coumaric acid, o-hydroxyphenylacetic acid, and protocatechuic acid, significantly repressed L-phenylalanine ammonia-lyase activity. The observed repression was not relieved by cyclic adenosine 5'-triphosphate.
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PMID:Regulation of L-phenylalanine ammonia-lyase from Rhizoctonia solani. 126 11

Injection of amylin (diabetes-associated peptide) into the hypothalamus induces anorexia, increases brain metabolism of dopamine and serotonin and elevates brain level of tryptophan. When male Sprague-Dawley rats were treated with 50 mg/kg L-tryptophan and L-tyrosine ethyl ester 30 min prior to the intrahypothalamic injection of 2 micrograms amylin, brain tryptophan and tyrosine levels were selectively increased as compared to rats treated with amylin alone. Hypothalamic and striatal serotonin metabolism also appeared to be increased following the amino acid-amylin treatment combination. These results suggest that amylin may increase transport of tyrosine and tryptophan into the brain, and that the increased availability of tryptophan may contribute to increased serotonin turnover observed following intrahypothalamic amylin treatment.
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PMID:Amylin increases transport of tyrosine and tryptophan into the brain. 128 Oct 37

The effect of protease inhibitors N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) and N-carbobenzoxy-L-phenylalanine chloromethyl ketone (ZPCK) at concentrations ranging from 1.5 x 10(-6) mol/l to 1.5 x 10(-4) mol/l on the specific binding of 3,5,3'-triiodothyronine (T3) to rat liver nuclear receptors was evaluated. Both TPCK at 1.5 x 10(-5) mol/l (P < 0.001) and ZPCK at 1.5 x 10(-6) mol/l (P < 0.05) showed the inhibition of T3 binding to nuclear receptors. The evaluation of T3 binding data following separation of unbound TPCK from treated nuclear receptors on a Sephadex G-25 column showed that the inhibition of T3 binding was irreversible, since a substantial decrease of the equilibrium association constant (Ka) was found when compared to the mock samples lacking TPCK. In addition, similar inhibitory effect on T3 specific binding to rat liver nuclear receptors was found at 5.0 x 10(-4) mol/l by protease substrates L-tyrosine benzyl ester (P < 0.001), L-tyrosine ethyl ester (P < 0.02), L-tryptophan methyl ester (P < 0.02) and L-tryptophan ethyl ester (P < 0.05). The data suggest that: 1. both protease inhibitors and substrates tested inhibited T3 specific binding to T3 nuclear receptors; 2. this may support the hypothesis that T3 receptors like other receptors encoded by c-erbA gene possess a site that recognize both serine protease inhibitors and substrates in its hormone binding domain.
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PMID:Effect of protease inhibitors and substrates on 3,5,3'-triiodothyronine binding to rat liver nuclear receptors. 130 55

The study concerned 72 schizophrenic and 200 depressed patients hospitalised between 1983 and 1990. The erythrocyte membrane transports (EMT) of L-tyrosine and L-tryptophan (at 37 degrees, 0 degrees and 37-0 degrees) of schizophrenics without treatment nor depression were different compared to controls and depressed patients. The schizophrenics under neuroleptic treatment and/or depressed showed same means of EMT values as depressed patients. The slopes of the correlations between EMT of tyrosine or tryptophan at 37 degrees, 0 degrees and 37-0 degrees, as well as that between plasma levels of these amino acids, were parallel. However the slopes of the correlations between EMT of tyrosine and tryptophan were different according to the subgroups of patients: the perturbations of EMT were related to the clinical characteristics. In depressed patients and in schizophrenic patients under neuroleptic treatment and/or depressed, little changes in EMT of tyrosine were related to high changes of EMT of tryptophan.
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PMID:[Erythrocyte membrane transport of amino acid precursors of monoamines in schizophrenic patients. Comparison with depressive patients]. 136 21

Tryptamine-4,5-dione (4,5-DKT) a neurotoxic derivative of serotonin (5-HT), was injected into the lateral ventricle of the rat in order to evaluate its biochemical effects. The levels of 8 substances in the hippocampus, striatum and prefrontal cortex were examined 3, 7 and 14 days after treatment with 4,5-DKT. 5-Hydroxytryptamine and 5-hydroxyindoleacetic acid (5-HIAA) levels were decreased in all three regions by days 7 and 14, respectively. Tryptamine-4,5-dione had no significant effect on dopaminergic or adrenergic systems or on the levels of L-tryptophan and L-tyrosine, in any of the three areas of brain examined. Reduced activity of tryptophan hydroxylase in the cortex was observed 14 days after administration of 4,5-DKT. However, administration of 4,5-DKT did not alter the binding of [3H]paroxetine, a specific antagonist of the uptake of 5-HT, to nerve terminals. These results indicate that 4,5-DKT produced depletion of 5-HT without eliminating serotoninergic nerve terminals.
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PMID:Neurochemical changes in the rat brain after intraventricular administration of tryptamine-4,5-dione. 137 72

1. The L-amino acid oxidase of the monocellate cobra (Naja naja kaouthia) venom was purified to electrophoretic homogeneity. The molecular weight of the enzyme was 112,200 as determined by Sephadex G-200 gel filtration chromatography, and 57,400 as determined by SDS-polyacrylamide gel electrophoresis. 2. The enzyme had an isoelectric point of 8.12 and a pH optimum of 8.5. It showed remarkable thermal stability, and, unlike many venom L-amino acid oxidase, was also stable in alkaline medium. The enzyme was partially inactivated by freezing. 3. The enzyme was very active against L-phenylalanine and L-tyrosine, moderately active against L-tryptophan, L-methionine, L-leucine, L-norleucine, L-arginine and L-norvaline. Other L-amino acids were oxidized slowly or not oxidized. 4. Kinetic studies suggest the presence of a side-chain binding site in the enzyme, and that the binding site comprises of at least four hydrophobic subsites.
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PMID:Purification and properties of the L-amino acid oxidase from monocellate cobra (Naja naja kaouthia) venom. 161 86

The impact of ultraviolet light on uv/vis absorption spectra of selected individual components of the cell breeding medium according to Eagle (MEM) was investigated. The strongest alterations of light absorption were detected in L-phenylalanine, L-tyrosine and L-tryptophan. Thus, the absorption behaviour of the Eagle (MEM) medium changed post radiation may be attributed to spectrophotometric alterations of absorption in aromatic amino acids. The results are discussed with regard to the effect on the surface charge of erythrocytes.
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PMID:[Effect of ultraviolet light on the UV/VIS absorption spectrum of components of Eagle (MEM) cell culture medium]. 169 77

The effect of a number of L-tyrosine (L-Tyr) analogues on L-Tyr uptake by B16/F10 malignant melanocytes is reported. This amino acid can be taken up by two of the most ubiquitous transport systems found in animals cells, L and presumably ASC. L-Tyr analogues devoid of the amino group, like p-hydroxyphenyl pyruvic acid and related compounds, and L-Tyr analogues devoid of the carboxyl group, such as tyramine, do not affect L-Tyr uptake. The other aromatic amino acids, L-Phe and L-Trp, and the L-Tyr analogues DL-m-Tyr, L-diiodotyrosine and L-dopa, strongly inhibit the uptake of L-Tyr. This suggests that these chemicals are transported more efficiently than L-Tyr. The ASC system does not show stereospecificity, but the L system has greater affinity for L-Tyr than for D-Tyr. The ASC system also has greater affinity for tyrosine isomers with the hydroxyl group in the ortho and meta positions. The presence of a methyl group at the alpha-carbon of L-Tyr and L-dopa also increases the affinity of the ASC system for these agents. In contrast, alpha-methylation decreases the affinity of the L system in comparison to L-Tyr. Finally, L-Tyr esters do not inhibit, but stimulate the transport of L-Tyr, mainly by the ASC system.
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PMID:Inhibition by analogues of L-tyrosine transport by B16/F10 melanoma cells. 182 66

The erythrocyte membrane transports (MT) of L-tyrosine and L-tryptophan, as well as their plasma levels, were measured in 143 depressed patients after a wash-out period of one week and before any antidepressant treatment, and then at regular intervals until they recovered. 49 normal subjects served as a control group. The perturbations of these biologic variables at baseline were different according to diagnostic groups (DSM III), compared to controls: significant decrease of the two MT in depressed bipolar disorders; significant decrease of MT in depressed bipolar disorders; significant decrease of MT tyrosine and significant increase of MT tryptophan in recurrent major depressions; no significant changes of MT in dysthymic disorders. The plasma levels of tyrosine and total tryptophan show a significant diminution in the 3 groups. The study of the evolution of these same variables after antidepressant treatment show a return to normal of the MT at recovery, as well as the plasma levels of tyrosine. The plasma levels of tryptophan stay low in depressed bipolar disorders and recurrent major depressions.
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PMID:[Plasma levels and membrane transports in red blood cell of tyrosine and tryptophane in depression. Evaluation at baseline and recovery]. 186 53

The main characteristics of L-tyrosine (L-Tyr) uptake by B16/F10 malignant melanocytes are reported. This amino acid can be taken up by two systems, both of them being saturable. The first one would be system L. This system can be studied in cells preloaded with amino acids that are a good substrate for system L, such as L-methionine or L-tryptophan. The kinetic parameters for L-Tyr uptake by this transport system are Vm = 6.5 pmol L-Tyr/10(3) cells.min and Km around 130 microM. The second system, probably the system ASC, shows lower capacity but higher affinity than the former. This system can be detected only in cells previously depleted of amino acids, showing approximate kinetic values of Vm 0.05 pmol L-Tyr/10(3) cells.min and Km around 5 microM. It is shown that the increase in cell density yields a decrease in the rate of L-Tyr uptake by system L, but this increase does not affect the high affinity system, alpha-MSH does not affect significantly the L-Tyr uptake by both systems. 2-Amino bicyclo-(2,2,1)-heptane-2-carboxylic acid produces a remarkable inhibition of the rate of L-Tyr uptake, but alpha-methylaminoisobutyric acid does not affect the rate of transport of this amino acid. The absence of sodium produces a slight but reliable decrease in the rate of L-Tyr uptake, supporting the involvement of two different transport systems. The ionophores monensin and nigericin enhance the transport by system L, but this effect is suppressed by the presence of ouabain. This finding indicates that the (Na+ -K+)-ATPase is essential for the stimulating action of ionophores.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transport of L-tyrosine by B16/F10 malignant melanocytes: characterization of the process. 198 30


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