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)

1. Modification with 2,4,6-trinitrobenzenesulphonic acid was studied for its effect on the structure, activity and response to regulatory effectors of ox liver glutamate dehydrogenase. 2. The modification affected amino groups only, and the relative reactivities of the amino groups of the enzyme are described. 3. A biphasic inactivation of the enzyme was observed and analysis of the course of inactivation and of modification showed that the rapid reaction of one amino group/subunit leads to loss of 80% of the enzymic activity. 4. NADH retarded the inactivation by 2,4,6-trinitrobenzenesulphonic acid, the protection increasing with NADH concentration. This, together with the previous observation, suggests that the rapidly reacting group is essential for the activity of the enzyme. 5. The effects of modification on the optical-rotatory-dispersion and sedimentation behaviour of the enzyme were studied. 6. The enzyme's response to the allosteric effector GTP was rapidly lost on modification, whereas its response to ADP was unaffected. Comparison of the inactivation and desensitization suggests that the reactive amino group is essential for both activity and GTP response, and that only a completely unmodified enzyme oligomer responds fully to GTP. 7. The merits of chemical-modification studies of large enzymes are discussed critically in connexion with the interpretation of these results.
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PMID:Chemical modification of glutamate dehydrogenase by 2,4,6-trinitrobenzenesulphonic acid. 430 31

1. Changes in the concentrations of ammonia, glutamine, glutamate, 2-oxoglutarate, 3-hydroxybutyrate, acetoacetate, alanine, aspartate, malate, lactate, pyruvate, NAD(+), NADH and adenine nucleotides were measured in freeze-clamped rat liver during ischaemia. 2. Although the concentrations of most of the metabolites changed rapidly during ischaemia the ratios [glutamate]/[2-oxoglutarate][NH(4) (+)] and [3-hydroxybutyrate]/[acetoacetate] changed equally and the value of the expression [3-hydroxybutyrate][2-oxoglutarate][NH(4) (+)]/[acetoacetate][glutamate] remained approximately constant, indicating that the 3-hydroxybutyrate dehydrogenase and glutamate dehydrogenase systems were at near-equilibrium with the mitochondrial NAD(+) couple. 3. The value of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] was about 0.7 in vivo and remained fairly constant during the ischaemic period of 5min, although the concentrations of alanine and oxoglutarate changed substantially. No explanation can be offered why the value of the ratio differed from that of the equilibrium constant of the alanine aminotransferase reaction, which is 1.48. 4. Injection of l-cycloserine 60min before the rats were killed increased the concentration of alanine in the liver fourfold and decreased the concentration of the other metabolites measured, except that of pyruvate. During ischaemia the concentration of alanine did not change but that of aspartate almost doubled. 5. After treatment with l-cycloserine the value in vivo of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] rose from 0.7 to 2.4. During ischaemia the value returned to 0.8. 6. The effects of l-cycloserine are consistent with the assumption that it specifically inhibits alanine aminotransferase. 7. Most of the alanine formed during ischaemia is probably derived from pyruvate and from ammonia released by the deamination of adenine nucleotides and glutamine. The alanine is presumably formed by the combined action of glutamate dehydrogenase and alanine aminotransferase. 8. The rate of anaerobic glycolysis, calculated from the increase in the lactate concentration, was 1.3mumol/min per g fresh wt. 9. Although the concentrations of the adenine nucleotides changed rapidly during ischaemia, the ratio [ATP][AMP]/[ADP](2) remained constant at 0.54, indicating that adenylate kinase established near-equilibrium under these conditions.
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PMID:Effects of ischaemia on metabolite concentrations in rat liver. 431 90

An affinity labeling reagent for the estrogenic-binding site of bovine liver L-glutamate dehydrogenase (EC 1.4.1.3) was prepared by conversion of diethylstilbestrol to its alkylating analogue, bromoacetyldiethylstilbestrol. Under standard assay conditions, the analogue acted as a reversible allosteric ligand with regulatory activity much like that of diethylstilbestrol. However, incubation of the enzyme with the alkylating agent in the presence of DPNH resulted in a permanent decrease in glutamate (X form) and an increase in alanine (Y form) activities, and in covalent attachment of diethylstilbestrol in the ratio of 1 mol per subunit (of particle weight 52,000). The brominated analogue behaved as an affinity label that mimicked the allosteric effects of diethylstilbestrol. Diethylstilbestrol protection of the enzyme against alkylation by bromoacetylated sterol suggested competition for the same binding site, while ADP protection indicated a shift of protein equilibrium into the X form. The diethylstilbestrol-enzyme compound was desensitized (relative to the native enzyme) to allosteric reagents such as ADP and GTP. The results were consistent with conformational freezing of the modified protein molecule into the Y form.
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PMID:Covalent attachment of diethylstilbestrol to glutamate dehydrogenase: implications for allosteric regulation. 432 3

1. Glutamate dehydrogenase was inhibited by l-serine O-sulphate, beta-chloro-l-alanine, O-phospho-l-serine and beta-chloro-l-alanine methyl ester. With the exception of beta-chloro-l-alanine methyl ester which was an irreversible inhibitor, it was possible to reverse the inhibitory effects by dialysis. 2. Both NAD(+) and glutamate afford some protection against the inhibition due to the methyl ester. No change in the normal stimulatory effect exhibited by ADP was observed in the presence of beta-chloro-l-alanine methyl ester but the effect due to GTP was modified. 3. Irradiation of glutamate dehydrogenase in the presence of Rose Bengal produced rapid inactivation. Amino acid analysis of the inactivated enzyme showed that eight histidine residues had been destroyed in the process.
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PMID:The inhibition of glutamate dehydrogenase by L-serine O-sulphate and related compounds and by photo-oxidation in the presence of Rose Bengal. 433 Nov 81

1. Glutamate dehydrogenase was subject to rapid inactivation when irradiated in the presence of Rose Bengal or incubated in the presence of ethoxyformic anhydride. 2. Inactivation in the presence of Rose Bengal led to the photo-oxidation of four histidine residues. Oxidation of three histidine residues had little effect on enzyme activity, but oxidation of the fourth residue led to the almost total loss of activity. 3. Acylation of glutamate dehydrogenase with ethoxyformic anhydride at pH6.1 led to the modification of three histidine residues with a corresponding loss of half the original activity. Acylation at pH7.5 led to the modification of two histidine residues and a total loss of enzyme activity. 4. One of the histidine residues undergoing reaction at pH6.1 also undergoes reaction at pH7.5. 5. The presence of either glutamate or NAD(+) in the reaction mixtures at pH6.1 had no appreciable effect. At pH7.5 glutamate caused a marked decrease in both the degree of alkylation and degree of inactivation. NAD(+) had no effect on the degree of inactivation at pH7.5 but did modify the extent of acylation. 6. The normal response of the enzyme towards ADP was unaffected by acylation at pH6.1 or 7.5. 7. The normal response of the enzyme towards GTP was altered by treatment at both pH6.1 and 7.5.
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PMID:The role of histidine residues in glutamate dehydrogenase. 434 75

1. The reaction of 4-iodoacetamidosalicylate with bovine liver glutamate dehydrogenase is dependent on pH. The pH-activity curve is bell-shaped and can be described by apparent pK values of 7.8+/-0.2 and 9.1+/-0.2. 2. Enzyme in which lysine-126 has been modified by 4-iodoacetamidosalicylate has unaltered sedimentation characteristics except when measured in the presence of GTP and NADH. 3. GTP binding to the inhibited enzyme is unaltered. However, GTP can no longer promote the binding of a second molecule of NADH, since this is already bound to the inhibited enzyme without GTP. 4. The equilibrium binding of ADP, GTP, NAD-sulphite and NADH (when measured at low concentrations) was largely unchanged by modification. 5. The number of binding sites for 2-oxoglutarate to the enzyme-NADH complex were decreased by 60% in an enzyme that has been inhibited by 70%.
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PMID:The effect of modifying lysine-126 on the physical, catalytic and regulatory properties of bovine liver glutamate dehydrogenase. 435 37

1. One mol of diethyl pyrocarbonate will react with one mol of glutamate dehydrogenase polypeptide chains to form one mol of N(1)-carbethoxyhistidine. Reaction is prevented by NADH. 2. The 1:1 complex has an increased specific activity (1.4-2.0-fold). 3. The reason for the activation is discussed. The results are not consistent with NADH dissociation from the enzyme-glutamate-NADH complex being rate-limiting in the steady state measured. 4. The effects of modification on the properties of the enzyme were investigated. The effects of GTP and NAD(+) on the enzyme activity are unaltered by activation. NADH binding is unaltered and there is no apparent change in the molecular weight. However, the activated enzyme can still be further activated by ADP. K(s) for ADP is decreased fivefold.
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PMID:The reaction of a histidine residue in glutamate dehydrogenase with diethyl pyrocarbonate. 435 38

When grown autotrophically in a thiosulfate-mineral salts medium, cells of the facultative chemoautotrophic bacterium, Thiobacillus novellus, produced two distinct glutamate dehydrogenases, one specific for nicotinamide adenine dinucleotide phosphate (NADP) and the other specific for nicotinamide adenine dinucleotide (NAD). When glutamate was supplied exogenously as the sole carbon source, the NAD-specific glutamate dehydrogenase was fully induced. Lower levels of the enzyme were found in bacteria grown in l-arginine, l-alanine, glucose, glycerol, lactate, citrate, or succinate. Arginine, histidine, and aspartate, on the other hand, caused a marked repression of the NADP-specific glutamate dehydrogenase activity. The NAD-dependent glutamate dehydrogenase was allosteric. Adenosine-5'-monophosphate and adenosine-5'-diphosphate acted as positive effectors. Both glutamate dehydrogenases were purified about 250-fold and were shown to be distinct protein with different physical properties.
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PMID:Evidence for two species of glutamate dehydrogenases in Thiobacillus novellus. 438 66

Ammonia assimilation has been investigated in four strains of Saccharomyces cerevisiae by measuring, at intervals throughout the growth cycle, the activities of several enzymes concerned with inorganic ammonia assimilation. Enzyme activities in extracts of cells were compared after growth in complete and defined media. The effect of shift from growth in a complete to growth in a defined medium (and the reverse) was also determined. The absence of aspartase (EC 4.3.1.1, l-aspartate-ammonia lyase) activity, the low specific activities of alanine dehydrogenase, glutamine synthetase [EC 6.3.1.2, l-glutamate-ammonia ligase (ADP)], and the marked increase in activity of the nicotinamide adenine dinucleotide phosphate-linked glutamate dehydrogenase (NADP-GDH) [EC 1.4.1.4, l-glutamate:NADP-oxidoreductase (deaminating)] during the early stages of growth support the conclusion that yeasts assimilate ammonia primarily via glutamate. The NADP-GDH showed a rapid increase in activity just before the initiation of exponential growth, reached a maximum at the mid-exponential stage, and then gradually declined in activity in the stationary phase. The NADP-GDH reached a higher level of activity when the yeasts were grown on the defined medium as compared with complete medium. The nicotinamide adenine dinucleotide-linked glutamate dehydrogenase (NAD-GDH) [EC 1.4.1.2, l-glutamate:NAD-oxidoreductase (deaminating)] showed only slight increases in activity during the exponential phase of growth. There was an inverse relationship in that the NADP-GDH increased in activity as the NAD-GDH decreased. The NAD-GDH activity was higher after growth on the complete medium. The glutamate-oxaloacetate transaminase (EC 2.6.1.1. l-aspartate:2-oxoglutarate aminotransferase) activity rose and fell in parallel with the NADP-GDH, although its specific activity was somewhat lower. Although other ammonia-assimilatory enzymes were demonstrable, it seems unlikely that their combined activities could account for the remainder of the ammonia-assimilatory capacity not accounted for by the NADP-GDH. The ability of aspartate to serve as effectively as glutamate as the sole source of nitrogen for the growth of yeast apparently resides in their ability to utilize aspartate for amino acid biosynthesis via transamination.
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PMID:Inorganic nitrogen assimilation in yeasts: alteration in enzyme activities associated with changes in cultural conditions and growth phase. 440 Apr 14

1. The binding of NAD(+) and NADP(+) to glutamate dehydrogenase has been studied in sodium phosphate buffer, pH7.0, by equilibrium dialysis. Approximate values for the dissociation constants are 0.47 and 2.5mm respectively. For NAD(+) the value agrees with that estimated from initial-rate results. 2. In the presence of the substrate analogue glutarate both coenzymes are bound more firmly, and there is one active centre per enzyme subunit. The binding results cannot be described in terms of independent and identical active centres, and binding is stronger at low coenzyme concentrations than at high concentrations. Either the six subunits of the oligomer are not identical or there are negative interactions between them in the binding of coenzymes in ternary complexes with glutarate. The latter explanation is favoured. 3. The binding studies support the conclusions drawn from earlier kinetic studies of the glutamate reaction. 4. ADP and GTP respectively decrease and increase the affinity of the enzyme for NAD(+) and NADP(+), in both the presence and absence of glutarate. The negative binding interactions in the presence of glutarate are abolished by ADP, which decreases the affinity for the coenzymes at low concentrations of the latter. 5. In the presence of glutarate, GTP and NAD(+) or NADP(+), the association of enzyme oligomers is prevented, and the solubility of the enzyme is decreased; the complex of enzyme and ligands readily crystallizes. 6. The results are discussed in relation to earlier kinetic studies.
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PMID:The binding of oxidized coenzymes by glutamate dehydrogenase and the effects of glutarate and purine nucleotides. 440 8


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