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)

Parts of the primary structure of the NAD-specific glutamate dehydrogenase [L-glutamate:NAD oxidoreductase (deaminating), EC 1.4.1.2] from Neurospora crassa are presented. Segments of the sequence representing 886 unique amino-acid residues have been determined; the largest contains 267 residues. There are only short regions of possible homology between this enzyme and the glutamate dehydrogenases of bovine liver or the NADP-specific enzyme of Neurospora. The large size of the subunit (116,000 molecular weight) of the NAD-specific glutamate dehydrogenase is unusual when compared to other known dehydrogenases.
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PMID:Partial amino-acid sequence of NAD-specific glutamate dehydrogenase of Neurospora crassa. 17 80

1. Initial rates of oxidative deamination of L-glutamate with NAD+ as coenzyme, and of reductive aminiation of 2-oxoglutarate with NADH as coenzyme, catalysed by bovine liver glutamate dehydrogenase were measured in 0.111 M-sodium phosphate buffer, pH 7, at 25 degrees C, in the absence and presence of product inhibitors. All 12 possible combinations of variable substrate and product inhibitor were used. 2. Strict competition was observed between NAD+ and NADH, and between glutamate and 2-oxoglutarate. All other inhibition patterns were clearly non-competitive, except for inhibition by NH4+ with NAD+ as variable substrate. Here the extrapolation did not permit a clear distinction between competitive and non-competitive inhibition. 3. Mutually non-competitive behaviour between glutamate and NH4+ indicates that these substrates can be bound at the active site simultaneously. 4. Primary Lineweaver-Burk plots and derived secondary plots of slopes and intercepts against inhibitor concentration were linear, with one exception: with 2-oxoglutarate as variable substrate, the replot of primary intercepts against inhibitory NAD+ concentration was curved. 5. Separate Ki values were evaluated for the effect of each product inhibitor on the individual terms in the reciprocal initial-rate equations. With this information it is possible to calculate rates for any combination of substrate concentrations within the experimental range with any concentration of a single product inhibitor. 6. The inhibition patterns are consistent with neither a simple compulsory-order mechanism nor a rapid-equilibrium random-order mechanism without modification. They can, however, be reconciled with either type of mechanism by postulating appropirate abortive complexes. Of the two compulsory sequences that have been proposed, one, that in which the order of binding is NADH, NH4+, 2-oxoglutarate, requires an implausible pattern of abortive complex-formation to account for the results. 7. On the basis of a rapid-equilibrium random-order mechanism, dissociation constants can be calculated from the Ki values. Where these can be compared with independent estimates from the kinetics of the uninhibited reaction or from direct measurements of substrate binding, the agreement is reasonable good. On balance, therefore, the results provide further support for the rapid-equilibrium random-order mechanism under these conditions.
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PMID:A product-inhibition study of bovine liver glutamate dehydrogenase. 17 78

Folates and tetrahydrofolates inhibit beef liver glutamate dehydrogenase (EC 1.4.1.2). Double reciprocal plats indicate a competitive inhibition for alpha-ketoglutarate-glutamate by folic acid and methotrexate and a complex or mixed type for NAD-NADH site. Pteroic acid is not inhibitory at the concentrations studied. The addition of up to four gamma-linked glutamyl residues to folic and tetrahydrofolic acids increases the inhibition. Further chain elongation of the gamma-peptide had no effect on the inhibitory activity. The p-aminobenzoate poly-gamma-glutamates were less inhibitory than the corresponding folyl polyglutamates.
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PMID:Folates as inhibitors of glutamate dehydrogenase. 17 72

The effects of phthalate esters on the oxidation of succinate, glutamate, beta-hydroxybutyrate and NADH by rat liver mitochondria were examined and it was found that di-n-butyl phthalate (DBP) strongly inhibited the succinate oxidation by intact and sonicated rat mitochondria, but did not inhibit the State 4 respiration with NAD-linked substrates such as glutamate and beta-hydroxybutyrate. However, oxygen uptake accelerated by the presence of ADP and substrate (State 3) was inhibited and the rate of oxygen uptake decreased to that without ADP (State 4). It was concluded that phthalate esters were electron and energy transport inhibitors but not uncouplers. Phthalate esters also inhibited NADH oxidation by sonicated mitochondria. The degree of inhibition depended on the carbon number of alkyl groups of phthalate esters, and DBP was the most potent inhibitor of respiration. The activity of purified beef liver glutamate dehydrogenase [EC 1.4.1.3] was slightly inhibited by phthalate esters.
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PMID:Effects of phthalate esters on the respiration of rat liver mitochondria. 18 66

Glutamate dehydrogenase (EC 1.4.1.2-4) has been purified and crystallized from the acetone powder of tuna liver. The enzyme has a molecular weight of 333 000 +/- 15 000 as evaluated by sedimentation equilibrium and constists of six identical subunits. Unlike the bovine enzyme the molecular weight does not increase with increasing protein concentration indicating that the tuna enzyme has no tendency to polymerize. The amino acid composition and peptide maps of the tuna and bovine liver enzyme are similar, suggesting considerable homology between the two enzymes. Furthermore, from the tryptic digest a hexadecapeptide containing a lysine residue reactive to pyridoxal 5'-phosphate exhibits the same composition and sequence as the peptide containing the reactive lysine-126 in the sequence of the bovine enzyme. The molecular activity is 25 and 510 mol of substrate per mol enzyme per s, respectively, for the glutamate oxidation and the alpha-ketoglutarate reduction with NAD or NADP as coenzymes. The enzyme is regulated by pyridine nucleotides like other vertebrate enzymes, but it also exhibits some coenzyme specificity, the activity being about fifteen times higher with NAD than with NADP.
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PMID:Purification, characteristics and sequence of a peptide containing an essential lysine residue. 18 70

Bovine liver glutamate dehydrogenase reacts rapidly with 2,3-butanedione to yield modified enzyme with 29% of its original maximum activity, but no change in its Michaelis constants for substrates and coenzymes. No significant reduction in the inactivation rate is produced by the addition of the allosteric activator ADP or inhibitor GTP, while partial protection against inactivation is provided by the coenzyme NAD+ or substrate 2-oxoglutarate when added separately. The most marked decrease in the rate of inactivation (about 10-fold) is provided by the combined addition of NAD+ and 2-oxoglutarate, suggesting that modification takes place in the region of the active site. Reaction with 2,3-butanedione also results in loss of the ability of the enzyme to be activated by ADP. Addition of ADP (but not NAD+, 2-oxoglutarate or GTP) to the incubation mixture protects markedly against the loss of activatability of ADP. It is concluded that 2,3-butanedione produces two distinguishable effects on glutamate dehydrogenase: a relatively specific modification of the regulatory ADP site and a distinct modification in the active center. Reaction of two arginyl residues per peptide chain appears to be responsible for disruption of the ADP activation property of the enzyme, while alteration of a maximum of five arginyl residues can be related to the reduction of maximum catalytic activity. Electrostatic interactions between the positively charged arginine groups and the negatively charged substrate, coenzyme and allosteric purine nucleotide may be important for the normal function of glutamate dehydrogenase.
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PMID:The importance of arginine residues in the catalytic and regulatory functions of bovine-liver glutamate dehydrogenase. 18 52

1)The time course of changes in concentration of renal metabolites in response to a non-toxic load of NH4 as NH4 Cl or NH4HCO3 were measured in fasted rats. 2) Following a NH4Cl load, decrease of renal concentration of 2-oxoglutarate occurs but this change is delayed in relation to the peak of the blood ammonia concentration and persists after disappearance of the hyperammoniemia. 3) Following a NH4HCO3 load, the oxoglutarate concentration changes are less marked and more transient. 4) No close relationship between the mitochondrial free NAD/NADH ratio calculated from the glutamate dehydrogenase and the 3-hydroxybutyrate dehydrogenase systems were seen during alteration of the ammonia concentration. 5) Contrary to the observations in the liver under similar circumstances (BROSNAN, J.T. et al.: Biochem.J. 138, 453, 1974), no increase in kidney tissue or renal venous blood alanine or aspartate concentration are seen. 6) A constant infusion of NH4HCO3 resulted only in an increase in tissue and renal venous blood glutamine concentration. 7) The infusion of NH4 together with a carbon source (malate) resulted in a similar increase in tissue glutamine concentration and more striking increase in renal venous glutamine concentration. No accumulation of aspartate nor alanine were seen. 8) In vitro studies indicate that the net flux through both the aspartate aminotransferase and the glutamate dehydrogenase reactions is dependent on the concentration of the reactants as expected for a near-equilibrium system. 9) It is concluded that the kidney response to an ammonia load differs from that of the liver despite the existence of a similar network of near-equilibrium reactions of (1) a lack of local availability of oxaloacetate, (2) a lower activity of alanine aminotransferase, (3) a greater in vivo activity of glutamine synthetase.
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PMID:Effect of an ammonia load on the kidney near-equilibrium systems in the rat in vivo. 18 80

The levels of several enzymes have been studied during sporulation of Saccharomyces cerevisia. The specific activities of ribonuclease and aminopeptidase I raised several-fold after transfer of the cells to sporulation medium, whereas the specific activities of phosphofructokinase, glucose-6-phosphate dehydrogenase, tryptophan synthase and pyruvate decarboxylase were not significantly altered. The specific activities of NAD-dependent glutamate dehydrogenase, isocitrate lyase, malate dehydrogenase and fructose bisphosphatase all decreased from the onset of sporulation. The inactivation of these latter enzymes was inhibited by cycloheximide and by inhibitors of energy metabolism. Hexokinase, alcohol dehydrogenase and glutamate oxaloacetate transaminase were partially lost from the cells during the period of ascus maturation. None of the enzyme changes observed proved to be 'sporulation-specific' in that it occurred exclusively in sporulating diploid yeast cells. Therefore it is postulated that the meiotic events and the metabolic changes required for ascospore formation are under separate genetic control in this organism. During sporulation, the cellular content of cytochromes b, c, and aa3 was reduced to 20% or less of that present in vegetative derepressed cells. Since the relative percentage of total to cycloheximide-insensitive mitochondrial protein synthesis was not significantly altered throughout sporulation, and the pattern of mitochondrially synthesized polypeptides was rather similar both in vegetative and in sporulating cells, it appeared that not only degradation but also synthesis and therefore turnover of the mitochondrially coded polypeptides of cytochromes b and aa3 took place during sporulation. The activity ratio of cytochrome c oxidase to F1-ATPase in submitochondrial particles isolated from vegetative cells and from purified asci was almost identical. This indicates that the loss of membrane-bound mitochondrial cytochromes during sporulation is probably due to a nonselective degradation of inner mitochondrial membrane proteins.
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PMID:Protein degradation during yeast sporulation. Enzyme and cytochrome patterns. 18 44

NAD+ with a nitroxide piperidine ring linked to the NH2 group of the adenine possesses full coenzymatic activity with glutamate dehydrogenase. Electron spin resonance spectra in the presence of glutamate dehydrogenase show mixtures of free and strongly immobilized spin-label. Binding studies in phosphate buffer demonstrate: (a) weak binary binding to the enzyme with a dissociation constant in the order of 2mM;(b) an indication for negative cooperativity or different sites for binding to enzyme-2-oxoglutarate, with dissociation constants in the order of 20--250muM; (c) similar but much weaker binding to enzyme-2-oxoglutarate-ADP; (d) a strong positive cooperative binding to enzyme-2-oxoglutarate-GTP, dependent on the enzyme concentration. Binding of phosphate to the enzyme with a Kd of about 20 mM or binding of pyrophosphate or tripolyphosphate with a Dd of about 2.5 mM enhances the binding of spin-labelled NAD+ in the presence of 2-oxoglutarate. There is evidence that the binding sites for these phosphates coincide with phosphate binding subsites of GTP.
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PMID:Binding studies of a spin-labelled oxidized coenzyme to bovine-liver glutamate dehydrogenase. 18 56

1. Computer averaging of multiple scans was used to refine the circular dichroism spectrum of bovine liver glutamate dehydrogenase, revealing well-defined structure in the aromatic region. 2. The circular dichroism of NAD+ bound to glutamate dehydrogenase is strongly negative at 260nm, probably owing to immobilization of the adenosine moiety. Loss of the characteristic adenine-nicotinamide interaction suggests that the coenzyme is bound in an unstacked conformation. 3. Glutarate and succinate, substrate analogues that are both inhibitors competitive with glutamate, do not significantly perturb the circular-dichroism spectrum of the enzyme in the absence of NAD+. 4. In the presence of NAD+, 150nM-succinate decreases the negative circular dichroism corresponding to bound coenzyme, but does not affect the protein circular dichroism. However, ISOmM-glutarate causes profound alternations of the circular-dichroism spectra of the bound NAD+ and of the enzyme, indicative of a protein conformational change. This direct evidence of conformational change specifically promoted by C5 dicarboxylates confirms the previous inference from protection studies. 5. The conformational change is discussed in relation to the allosteric mechanism of glutamate dehydrogenase.
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PMID:The allosteric mechanism of bovine liver glutamate dehydrogenase. Evidence from circular-dichroism studies for a conformational change in the ternary complex enzyme-(oxidized nicotinamide-adenine dinucleotide)-glutarate. 19 83


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