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

Two aminotransferases from Escherichia coli were purified to homogeneity by the criterion of gel electrophoresis. The first (enzyme A) is active on L-aspartic acid, L-tyrosine, L-phenylalanine, and L-tryptophan; the second (enzyme B) is active on the aromatic amiono acids. Enzyme A is identical in substrate specificity with transaminase A and is mainly an aspartate aminotransferase; enzyme B has never been described before and is an aromatic amino acid aminotransferase. The two enzymes are different in the Vmax and Km values with their common substrates and pyridoxal phosphate, in heat stability (enzyme A being heat-stable and enzyme B being heat-labile at 55 degrees) and in pH optima with the amino acid substrates. They are similar in their amino acid composition, each enzyme appears to consist of two subunits, and enzyme B may be converted to enzyme A by controlled proteolysis with subtilsin. The conversion was detected by the generation of new aspartate aminotransferase activity from enzyme B and was further verified by identification by acrylamide gel electrophoresis of the newly formed enzyme A. The two enzymes appear to be products of two genes different in a small, probably terminal, nucleotide sequence.
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PMID:Multispecific aspartate and aromatic amino acid aminotransferases in Escherichia coli. 23 11

1. Dexamethasone phosphate causes approximately a threefold increase of the tyrosine-alpha-ketoglutarate transaminase in the culture of RLC cells. 2. The induction of the enzyme depends on the presence of L-tyrosine. Omission of L-leucine or L-tryptophan, respectively, has no effect. 3. Omission of L-tyrosine influences the activity of the lactate dehydrogenase and malate dehydrogenase not at all and that of the glucose-6-phosphate-dehydrogenase only to a small extent. 4. In the absense of L-tyrosine an superinduction takes also place by actinomycin.
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PMID:[The importance of the substrate for the induction of tyrosine-alpha-ketoglutarate-transaminase in RLC-cells (author's transl)]. 24 Feb 38

Chymotrypsinogen A and alpha-chymotrypsin are both nitrated at tyrosines 146 and 171 by reaction with tetranitromethane. This substitution was essentially without influence on the overall rate constant for hydrolyses of N-acetyl-L-tryptophan methyl ester and N-acetyl-L-tyrosine ethyl ester catalyzed by alpha-chymotrypsin and delta-chymotrypsin, prepared by fast tryptic activation of nitrated chymotrypsinogen. With both ester substrates Km was doubled for nitrated alpha-chymotrypsin. Nitrated alpha-chymotrypsin, nitrated delta-chymotrypsin and delta-chymotrypsin could all bind N-acetyl-L-tryptophan methyl ester at alkaline pH, in contrast to alpha-chymotrypsin. The dissociation constant, Kd, of the complex of alpha-chymotrypsin and basic pancreatic trypsin inhibitor was lowered ten-fold relative to the constant obtained with unmodified alpha-chymotrypsin. The nitrated delta-chymotrypsin and delta-chymotrypsin showed identical Kd values. The nitrated alpha-chymotrypsin is inactivated faster at pH 8.0 and 8.5 than alpha-chymotrypsin and apparently by a different mechanism.
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PMID:Enzymic properties of nitrated alpha-chymotrypsin and delta-chymotrypsin. 24 45

A recent paper [Chibber, B. A. K., Tomich, J. M., Mertz, E. T. & Viswanatha, T. (1977) Proc. Natl. Acad. Sci. USA 74, 510-514] presented evidence that was taken to support the existence of an intermediate in the deacetylation of acetylchymotrypsin. It was observed that deacylation, as measured by following the decrease in [(14)C]acetylchymotrypsin (decrease in acid-precipitable radioactivity), occurred at 1/10 the rate of reactivation, as measured by return of activity toward N-acetyl-L-tyrosine ethyl ester. Our experiments have shown that, at pH 6, the deacylation rate constant (measured by the loss of [(14)C]acetylchymotrypsin and by the formation of [(14)C]acetate) is identical (within experimental error) with the rate constant for reactivation (measured by determining the activity of aliquots of reactivating enzyme against N-acetyl-L-tryptophan ethyl ester) and with K(cat) for the turnover of p-nitrophenyl acetate by alpha-chymotrypsin. Part of the 10-fold greater reactivation rate observed by Chibber et al. has been shown to be due to the presence of 10% (vol/vol) isopropanol in their reactivation mixture, and it is argued that the balance of the effect is a manifestation of the "indole effect" produced by the simultaneous presence of 10 mM N-acetyl-L-tyrosine ethyl ester throughout the reactivation experiments. The results presented are entirely consistent with the three-step mechanism of catalysis by alpha-chymotrypsin and negate the existence of the proposed additional acetyl-enzyme intermediate.
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PMID:Absence of evidence for an intermediate in the deacetylation of acetylchymotrypsin. 27 31

Administration of L-tyrosine to normotensive or spontaneously hypertensive rats reduces blood pressure. The effect is maximal within 2 hr of injection. In spontaneously hypertensive rats, a dose of 50 mg/kg, intraperitoneally, reduces blood pressure by about 12 mm Hg (1 mm Hg = 1.33 x 10(2) pascals); a dose of 200 mg/kg produces the maximal effect, a reduction of about 40 mm Hg. Tryptophan injection (225 mg/kg) also lowers blood pressure in spontaneously hypertensive rats, but only by about half as much as an equivalent dose of tyrosine. Other amino acids tested (leucine, isoleucine, valine, alanine, arginine, and aspartate) do not affect blood pressure. Tyrosine injection appears to reduce blood pressure via an action within the central nervous system, since the effect can be blocked by co-administering other large neutral amino acids that reduce tyrosine's uptake into the brain. That tyrosine's antihypertensive action is mediated by an acceleration in norepinephrine or epinephrine release within the central nervous system is suggested by the concurrent increase that its injection produces in brain levels of methoxyhydroxyphenylethylglycol sulfate.
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PMID:Tyrosine administration reduces blood pressure and enhances brain norepinephrine release in spontaneously hypertensive rats. 29 Oct 18

The present paper reviews our recents studies on the plastein reaction applied to improve nutritional quality of conventional and unconventional proteins, with special emphasis on the papaincatalyzed incorporation of essential amino acids (used in ethyl ester form) into the proteins : L-methionine into soybean protein, L-lysine into wheat gluten and L-tyrosine into fish protein (after removal of phenylalanine). The paper deals also with an attempt to improve proteins extracted from the photosynthetic microorganisms, Spirulina maxima (a blue-green alga), Rhodopseudomonas capsulatus (a non-sulfur purple bacterium) and Trifolium repens L. (a type of white clover) by way of incorporating simultaneously the three amino acids, L-methionine, L-lysine and L-tryptophan. This process, when properly carried out, can produce plasteins whose essential amino acid patterns have approximated the FAO/WHO suggested pattern (1973). Besides the plastein reaction, its novel modification has been developed, which will be more conveniently applied to a larger-scale process for the amino acid incorporation. A brief discussion is added in this regard.
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PMID:Nutritional improvement of food proteins by enzymatic modification, especially by plastein synthesis reaction. 36 Sep 51

An in vitro system was developed to detect antimetabolites in fermentation liquors of soil microorganisms. This system effectively uncovers antimetabolites of purines and pyrimidines and of selected amino acids with established differences in their biosynthesis by normal cells versus certain malignant cells. Currently these amino acids include: L-asparagine, L-aspartic acid, L-glutamine, L-cysteine (cystine), L-methionine, L-arginine, L-histidine, L-tyrosine, L-phenylalanine, L-tryptophan, L-threonine, and L-serine. It is expected that these antimetabolites could be useful either alone or in combination with specific depleting enzymes in the treatment of malignancies where such an imbalance was established.
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PMID:In vitro system for detection of antimetabolites of specific amino acids. 46 52

Dietary amino acid regimens designed to enhance catecholaminergic and serotonergic functioning were found to differentially affect territorial-induced attacks in mice. Male albino mice were maintained on a semi-synthetic 12% casein protein diet for 2 weeks, then switched to diets modified by the addition of a 4% L-amino acid supplement, or 4% casein (control). Measures of aggressive behavior and open-field locomotor activity were obtained before and after the dietary supplements were administered. Resident mice fed supplements of L-tyrosine displayed a marked increase in the number of attacks on intruders and shorter attack latencies, but their locomotor activity was unaffected. L-phenylalanine supplements alone or in combination with L-tyrosine reduced the latency to attack and increased motility but did not affect the number of attacks. As a whole, the group of animals fed L-tryptophan showed no changes in aggression or motility.
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PMID:Effects of dietary tyrosine, phenylalanine, and tryptophan on aggression in mice. 56 Jun 99

The biosynthesis of the antitumor antibiotic sibiromycin by Streptosporangium sibiricum requires the construction of four units: the amino sugar from glucose; the anthranilate ring from DL-tryptophan probably via kynurenine; the aromatic methyl group from methionine; the propylidene proline from L-tyrosine with the loss of two aromatic carbons and addition of a C-1 from methionine. Retention of tritium from DL-[5-3H]tryptophan in sibiromycin suggest an NIH shift during hydroxylation of an intermediate.
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PMID:Pyrrolo[1,4]benzodiazepine antibiotics. Biosynthesis of the antitumor antibiotic sibiromycin by Streptosporangium sibiricum. 58

An enzyme deacylating preferentially N-acyl-L-aromatic amino acids was partially purified from rat kidney. The purification procedure included DEAE-cellulose column chromatography, (NH4)2SO4 fractionation, gel-filtration on a Sephadex G-200 column and further DEAE-cellulose chromatography. The enzyme was thus separated from aminoacylase (N-acylamino-acid amidohydrolase, EC 3.5.1.14) (acylase I). Although the enzyme preparation contained other acylases, the experimental data (effect of p-chloromercuric benzoate, heat stability and inhibition between substrates) suggest that the enzyme acts preferentially on N-acyl derivatives of L-tryptophan, L-tyrosine, L-phenylalanine and L-histidine. This enzyme appears to be present in many animal tissues.
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PMID:N-Acyl-L-aromatic amino acid deacylase in animal tissues. 62 89


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