Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.4.1.2 (glutamate dehydrogenase)
4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel two-step enzyme-linked assay for aminopeptidase W is described and validated by comparison with other assays. L-alpha-Glutamyl-L-tryptophan (Glu-Trp) is a favoured substrate for this enzyme. With the use of glutamate dehydrogenase (EC 1.4.1.2) in a second step, the assay measured the release of free glutamate from L-alpha-glutamyl-L-tryptophan by the increase in NADH fluorescence. In the presence of 5 mM-1,10-phenanthroline and 50 microM-cilastatin the contribution of other membrane peptidases, in particular aminopeptidases N and A and microsomal dipeptidase in kidney, was very small. Residual cytosolic activities hydrolysing Glu-Trp were sensitive to inhibition by 2.5 mM-N-ethylmaleimide. The activity of aminopeptidase W was unaffected by these inhibitors. There was good correlation between the fluorimetric assay and those in which the free tryptophan released by kidney membrane fractions was determined by h.p.l.c. or the aminopeptidase W was measured immunoradiometrically with a monoclonal antibody.
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PMID:A fluorimetric assay for aminopeptidase W. 342 47

1. The tryptophan requirement of rainbow trout (initial body wt, 13 g) was estimated by feeding diets containing varied levels of tryptophan from 0.06 to 0.5% of diet for 6 weeks. 2. The estimated tryptophan requirement was 0.20-0.25 (0.57-0.71)% of diet (dietary proteins). 3. Nitrogen retention increased and feed/gain decreased with dietary tryptophan levels up to 0.14%, but no further effect was observed at levels above 0.14%. 4. Carcass protein content gradually increased and lipid and ash contents decreased with increasing dietary tryptophan levels. 5. Dietary tryptophan levels did not affect hepatosomatic index or liver glutamate dehydrogenase activity.
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PMID:Effects of dietary tryptophan levels on growth, feed/gain, carcass composition and liver glutamate dehydrogenase activity in rainbow trout (Salmo gairdneri). 342 11

Photooxidation of bovine liver glutamate dehydrogenase (GDH, EC 1.4.1.3) in the presence of methylene blue at a low light intensity occurs in two stages. At the first stage, the duration of which depends on temperature and dye concentration, a slight activation is observed simultaneously with the oxidation of two histidine residues. At the second stage, the inactivation is concomitant with the oxidation of three histidine and one tryptophan residues. The inactivation is a first order reaction (k = 3,22 X 10(-2) min-1) and is correlated with changes in the circular dichroism spectra. These data testify to the structural role of histidine residues in the GDH molecule. The kinetic behaviour of GDH during its modification with diethylpyrocarbonate (DEP) depends on pH and the reagent concentration. Four histidine residues undergo carbethoxylation at pH 6.0 and 7.5, but the modification rate is much higher at pH 7.5. At low DEP concentrations, a remarkable activation is observed with a simultaneous modification of one histidine residue, which is independent of pH. At high DEP concentrations, a rapid inactivation takes place at pH 7.5. Treatment of the carbethoxylated inactive enzyme with hydroxylamine results in the deacylation of histidine residues without any noticeable reactivation. The data on the combined effect of DEP and pyridoxal-5'-phosphate suggest that GDH inactivation by DEP at pH 7.5 is a result of modification of an essential epsilon-NH2 group of lysine-126.
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PMID:[Structural role of histidine residues in NAD(P)-glutamate dehydrogenase from the bovine liver]. 407 86

1. The NADP-dependent glutamate dehydrogenase of Neurospora crassa undergoes slow reversible structural transitions, with half-times in the order of a few minutes, between active and inactive states. The inactive state of the enzyme, which predominates at pH values below 7.0, has an intrinsic tryptophan fluorescence 25% lower than that of the active state, which predominates at pH values above 7.6. The inactive state can be activated either by an increase in pH or by addition of activators such as succinate. 2. The kinetics of the slow transitions that follow activating and inactivating rapid changes in conditions have been monitored by measurements of protein fluorescence. The results show that the slow reversible conformational change detected by the change in fluorescence is the rate-limiting process for enzyme activation and inactivation. 3. In both directions this conformational change follows apparent first-order kinetics and the rate constant is independent of protein concentration. These kinetics and published measurements of molecular weight are indicative of an isomerization process. 4. In both directions the changes show a large energy of activation and a large positive entropy of activation, consistent with a considerable disturbance of conformation in the transition state. 5. Comparisons of the fluorescence emission spectra of the active and inactive states indicate that the difference in fluorescence is produced by quenching, possibly intramolecular, in the inactive conformation. Iodide ions cause similar quenching. 6. In some mutationally altered forms of the enzyme comparable but modified conformational changes can be followed by protein fluorescence.
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PMID:Slow conformational changes of a Neurospora glutamate dehydrogenase studied by protein fluorescence. 415 26

The am locus of Neurospora codes for NADP-dependent glutamate dehydrogenase (GDH). Four new am mutants that produced mutationally altered GDH have been characterized. Mutant am119 is a CRM-negative, complementing mutant that maps between am2 and am1. The other three mutants are CRM formers that produce varieties of GDH that can be activated by glutamate or succinate. The GDH of am130 and am131 is similar in terms of activation properties to that of am3. The GDH of am122 requires very high concentrations of dicarboxylate for activity. The mutation in am130 maps between am14 and am2 and resulted in a replacement at residue 75 of the GDH (pro leads to ser). The mutation in am122 maps near am11 and apparently resulted in the replacement of the tryptophan residue at position 389 with an unknown amino acid. The mutation in am131 maps between am2 and am1.
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PMID:New mutational variants of Neurospora NADP-specific glutamate dehydrogenase. 645 73

Pulse radiolysis and 60Co gamma radiolysis were used to study the effects of ionizing radiations on the activity of glutamate dehydrogenase. Hydroxyl radicals are considerably more effective than hydrated electrons in causing loss of enzymatic activity. Evidence is also presented that the free radical anions (SCN)-.2, (Br)-.2, and (I)-.2 react with the enzyme and cause a loss of enzymatic activity. The results implicate the possible involvement of cysteine, tyrosine, and tryptophan residues in the activity of glutamate dehydrogenase.
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PMID:The radiation inactivation of glutamate dehydrogenase. 682 10

Protease B [EC 3.4.22.9] was purified from baker's yeast by plasmolysis of yeast, acid activation, acid precipitation, and column chromatographies on QAE-Sephadex, SP-Sephadex, D-tryptophan methyl ester-Sepharose 4B and Sephadex G-100. The purified enzyme was inhibited by phenylmethylsulfonyl fluoride and sulfhydryl-blocking reagents. Chymostatin and antipain at extremely low concentrations (1 micro M) inhibited the protease B. The effects of the enzyme on various yeast enzymes were examined by measuring their inactivation. The enzyme inactivated 6-phosphogluconate dehydrogenase [EC 1.1.1.44] and uricase [EC 1.7.3.3], but not malate dehydrogenase [EC 1.1.1.37], alcohol dehydrogenase [EC 1.1.1.1], glutamate dehydrogenase [EC 1.4.1.3], glucose-6-phosphate dehydrogenase [EC 1.1.1.49] or hexokinase [EC 2.7.1.1].
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PMID:Purification and characterization of yeast protease B. 699 57

Fed and fasted rats were injected with L-tryptophan (12.5 mg/100 g body weight) and the specific activities of L-glutamic: NAD oxidoreductase (deaminating) (EC 1.4.1.2) (GDH), L-aspartic-2-ketoglutaric aminotransferase (EC 2.6.1.1) (GOT) and L-alanine-2-ketoglutaric aminotransferase (EC 2.6.1.2) (GPT) from hepatic mitochondria and cytosol were compared. L-tryptophan results in a decrease of mitochondrial GDH activity by 22% and of cytosolic GPT and GOT by 42% and 38% respectively in the liver of fasted rats. Xanthurenate is a potent inhibitor of purified extramitochondrial GPT, whereas anthranilate and quinolinate are less potent inhibitors. L-tryptophan, 5-OH-tryptophan and indole exert a slight inhibition. Kynurenine, 5-OH-tryptamine, tryptamine, picolinic acid, nicotinic acid and indoloacetic acid do not show any inhibition of GPT. It is suggested that L-tryptophan injection inhibits extramitochondrial GPT by its transformation to xanthurenate and anthranilate.
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PMID:Effect of L-tryptophan injection in rats on some enzymes of amino acid metabolism in liver. I. In vitro studies of the effect of L-tryptophan and its metabolites on the extramitochondrial L-alanine: 2-ketoglutaric aminotransferase. 722 74

Porphyrin-induced photodamage has been studied on small organic molecules, biomolecules, mitochondria and red cells. Water soluble components (e.g. tryptophan and glutamate dehydrogenase) are more easily destroyed by uroporphyrin than by protoporphyrin. On the other hand, lipophilic components (e.g. succinate dehydrogenase, mitochondria and red cell membranes) are more severely damaged by protoporphyrin. The results may be of importance to explain the different skin lesions in erythropoietic protoporphyria and in porphyria cutanea tarda. The photodamage is enhanced by D2O and reduced by azide. Reagents known to increase or decrease the yields of superoxide, peroxide or hydroxyl radicals have no effect on the photodamage. The results suggest that singlet oxygen is the most important reactive oxygen species.
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PMID:Porphyrin-induced photodamage at the cellular and the subcellular level as related to the solubility of the porphyrin. 747 96

This study is concerned with the structural characterization in solution of the glutamate dehydrogenase from the Archaeon Sulfolobus solfataricus. At neutral pH both alpha-helix and beta-sheet constitute the secondary structure of this enzyme, on the basis of circular dichroism. A complex, temperature dependent self-association equilibrium regulates the formation of the enzyme quaternary structure, which seems to be accompanied by a reversible structural change. At 25 degrees C the enzyme is mostly represented by monomeric subunits at concentrations lower than 0.02 mg/ml, while oligomers are predominant at concentrations higher than 0.12 mg/ml. The mid-point of the association curve shifts from 0.05 mg/ml at 25 degrees C to about 0.1 mg/ml at 45 degrees C. Only the oligomeric form appears to be temperature resistant. Monomeric and oligomeric enzyme show distinct behaviour on guanidine hydrochloride perturbation at neutral pH. The monomer denaturation, although complex, is reversible. Two fluorescent tryptophan classes are detectable in the monomer, monitoring the independent unfolding of two regions through a multistate transition. Instead, the oligomeric protein shows a complex denaturation pattern with the tendency to aggregate irreversibly at high denaturant concentration.
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PMID:Molecular properties of glutamate dehydrogenase from the extreme thermophilic archaebacterium Sulfolobus solfataricus. 766 6


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