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)

Nuclear glutamate dehydrogenase (EC 1.4.1.3) activity has been demonstrated in Chinese hamster ovary cells. Some characteristics of this enzyme have been examined and compared with those of the mitochondrial glutamate dehydrogenase from the same source. Differences were detected in the extent of the activation by inorganic phosphate, in the pH versus activity curves, in the affinity of the two enzymes for the cofactor NAD+ and in the electrophosretic mobility. A different rate of decay of the two enzymes has been observed in cells grown in the presence of chloramphenicol. Immunological studies show that, as in ox liver, the nuclear enzyme has specific antigenic determinants besides those in common with mitochondrial glutamate dehydrogenase. Finally, experiments of thermal inactivation indicate a higher stability of the mitochondrial enzyme.
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PMID:Mitochondrial and nuclear glutamate dehydrogenases in Chinese hamster ovary cells in culture. 5 7

The isolation and sequences of an additional 80 peptides from a tryptic digest of the NAD-specific glutamate dehydrogenase of Neurospora crassa are reported. These include an additional peptide containing a lysine residue labeled at the epsilon-amino group with pyridoxal 5'-phosphate. The sequence of this peptide shows some homology with the reactive lysine residue of other glutamate dehydrogenases.
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PMID:Nicotinamide adenine dinucleotide-specific glutamate dehydrogenase of Neurospora. V. Tryptic peptides. 14 34

The effects of KCl-induced cardiac arrest on the redox state of the fluorescent flavoproteins and nicotinamide nucleotides and on that of cytochromes c and a were studied by surface fluorometric and reflectance spectrophotometric methods. These changes were compared with measurements of the concentrations of the adenylate system, creatine phosphate, some intermediates of the tricarboxylic acid cycle and reactants of the glutamate dehydrogenase system. KCl-induced cardiac arrest caused reduction of the fluorescent flavoproteins and nicotinamide nucleotides, oxidation of cytochromes c and a, inhibition of oxygen consumption and an increase in the ATP/(ADP X Pi) ratio. The increase in the latter was due mainly to a decrease in the concentration of Pi and an equivalent increase in creatine phosphate. The cytochromes c and a were maintained at equal redox potential and changed in parallel. When the redox state of the mitochondrial NAD couple was calculated from the glutamate dehydrogenase equilibrium, the free energy change (deltaG) corresponding to the potential difference between the NAD couple and cytochrome c was 115.8 kj/mol in the beating heart and 122.2 kj/mol in the arrested heart. The deltaG values of ATP hydrolysis calculated from the concentrations of ATP, Pi and ADP, corrected for bound ADP, were 111.1 kj/2 mol and 115.4 kj/2 mol in the beating and arrested heart respectively. The accumulation of citrate and the direction of the redox changes in the respiratory carriers indicate that the tricarboxylic acid cycle flux is controlled by the respiratory chain. The data also show a near equilibrium between the electron carriers and the adenylate system and suggest that the equilibrium hypothesis of mitochondrial respiratory control is applicable to intact myocardial tissue.
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PMID:Respiratory control in isolated perfused rat heart. Role of the equilibrium relations between the mitochondrial electron carriers and the adenylate system. 17 32

The time-course of inactivation of bovine liver glutamate dehydrogenase by pyridoxal 5'-phosphate was studied in the presence of varied amounts of 2-oxoglutarate or NADH. Pseudo-first-order analysis reveals that the protection by both these compounds is competitive with respect to the chemical modifier. The competition is only partial, however: saturation with either NADH or 2-oxoglutarate decreases the rate constant for inactivation to a finite minimum and not to zero. Similarly, the plot of activity at equilibrium as a function of the concentration of the protecting substrate or coenzyme reveals that neither NADH nor 2-oxoglutarate protects completely against inactivation. In initial-rate experiments, pyridoxal 5'-phosphate, used as an instantaneous inhibitor rather than a long-term inactivator, displayed non-competitive inhibition with respect to both 2-oxoglutarate and NADH. These results clearly indicate that, although there is mutual hindrance between the binding to the enzyme of pyridoxal 5'-phosphate, on the one hand, and 2-oxoglutarate or NADH on the other, binding is not mutually exclusive. These findings are discussed in terms of the two-step mechanism for inactivation by pyridoxal 5'-phosphate. It is concluded that lysine-126 cannot be solely responsible for binding either the substrate or the coenzyme, but could be essential for the catalytic step.
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PMID:Ox liver glutamate dehydrogenase. The role of lysine-126 reappraised in the light of studies of inhibition and inactivation by pyridoxal 5'-phosphate. 17 93

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

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

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. Intact and pure parenchymal and non-parenchymal cells were isolated from rat liver. The specific activities of several mitochondrial enzymes were determined in both parenchymal and non-parenchymal cell homogenates to characterize the mitochondria in these liver cell types. 2. In general the activities of mitochondrial enzymes were lower in non-parenchymal liver cells than in parenchymal cells. The specific activity of pyruvate carboxylase in non-parenchymal cells expressed as the percentage of that in parenchymal cells was onlu 2% for glutamate dehydrogenase 4.3% and for cytochrome c oxidase 79.4%. Monoamine oxidase, as an exception, has an equal specific activity in both cell types. 3. The activity ratio of pyruvate carboxylase at 10 mM pyruvate over 0.1 mM pyruvate is 3.35 for parenchymal cells and 1.50 for non-parenchymal cells. This indicates that non-parenchymal liver cells only contain the high affinity form of pyruvate carboxylase in contrast to parenchymal cells. 4. The ratio of glycerol-3-phosphate cytochrome c reductase over succinate cytochrome c reductase activity differs from parenchymal (0.01) and non-parenchymal cells (0.10). This might indicate that the glycerol-3-phosphate shuttle, which is important for the transport of reduction equivalents for cytosol to mitochondria is relatively more active in non-parenchymal cells than in parenchymal cells. 5. The activity pattern of mitochondrial enzymes in parenchymal and non-parenchymal cell homogenates indicates that these cell types contain different types of mitochondria. The presence of these different cell types in liver will therefore contribute to the heterogeneity of isolated rat liver mitochondria in which the mitochondria from non-parenchymal cells might be considered as "non-gluconeogenic".
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PMID:Different types of mitochondria in parenchymal and non-parenchymal rat-liver cells. 19 9

A procedure has been developed for isolating nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (am) mutants of Neurospora. Physiological, genetic, and enzymatic tests show that the new mutants are am alleles. Reconstruction tests and analysis of the new alleles show that the procedure yields a broad spectrum of lesions at the am locus. The isolation of am mutants by this technique appears to be related to the effect of am mutants on the control of the general permease.
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PMID:Direct selective procedure for isolating Neurospora mutants defective in nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase. 20 Jun 2

The NAD-dependent glutamate dehydrogenase from Candida utilis was isolated from 32P-labeled cells following enzyme inactivation promoted by glutamate starvation and found to exist in a phosphorylated form. Analysis of purified, fully active NAD-dependent glutamate dehydrogenase (a form) and inactive NAD-dependent glutamate dehydrogenase (b form) for alkalilabile phosphate revealed that the a form contained 0.09 +/- 0.06 mol of phosphate/mol of enzyme subunit and b form 1.25 +/- 0.06 mol of phosphate/mol of enzyme subunit. Phosphorylation caused a 10-fold reduction in enzyme specific activity. Dephosphorylation (release of 32P) and enzyme reactivation occurred on incubation with cell-free yeast extracts, indicating the presence of a phosphoprotein phosphatase in such preparations.
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PMID:Phosphorylation of NAD-dependent glutamate dehydrogenase from yeast. 20 32


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