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)

L-Glutamine, when purified free of traces of NH4+ present in solution, does not act as an alternative substrate to NH4+ for the NADP-specific glutamate dehydrogenase of Neurospora. L-Glutamine interferes with detection of small quantities of NH4+ by Nessler's reagent. L-Asparagine is not an alternative substrate to NH4+ for this enzyme.
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PMID:Re-investigation of the effects of L-glutamine and L-asparagine on the Neurospora crassa NADP-specific glutamate dehydrogenase. 13 20

The final products of the arginine catabolism that can be utilized as a nitrogen source in Neurospora crassa are ammonium, glutamic acid, and glutamine. The effect of these compounds on arginase induction by arginine was studied. In wild-type strain 74-A, induction by arginine was almost completely repressed by glutamic acid plus ammonium, whereas ammonium or glutamic acid alone had only moderate effects. Arginine products of catabolism also repressed arginase induction. A mutant, ure-1, which lacks urease activity, hyperinduced its arginase with arginine as a nitrogen source. The addition of either ammonium or glutamine produced effects similar to those in the wild-type strain. The effect of ammonium on arginase induction is mediated through its conversion into glutamine. This was demonstrated in mutant am-1, which lacks L-glutamate dehydrogenase activity. In this mutant, the effect of glutamic acid was reduced, and, with ammonium, it was completely lost. The addition of glutamine or glutamic acid plus ammonium to this strain decreased by threefold the induction of arginase by arginine. Proline, a final product of arginine catabolism, competitively inhibited arginase activity. This effect and the repression of arginase by glutamine are examples of negative modulation of the first enzyme in a catabolic pathway by its final products.
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PMID:Nitrogen regulation of arginase in Neurospora crassa. 14 62

Synthesis of wild-type Neurospora crassa assimilatory nitrate reductase is induced in the presence of nitrate ions and repressed in the presence of ammonium ions. Effects of several Neurospora mutations on the regulation of this enzyme are shown: (i) the mutants, nit-1 and nit-3, involving separate lesions, lack reduced nicotinamide adenine dinucleotide (NADPH)-nitrate reductase activity and at least one of three other activities associated with the wild-type enzyme. The two mutants do not require the presence of nitrate for induction of their aberrant nitrate reductases and are constitutive for their component nitrate reductase activities in the absence of ammonium ions. (ii) An analog of the wild-type enzyme (similar to the nit-1 enzyme) is formed when wild type is grown in a medium in which molybdenum has been replaced by vanadium or tungsten; the resulting enzyme lacks NADPH-nitrate reductase activity. Unlike nit-1, wild type produced this analog only in the presence of nitrate. Contaminating nitrate does not appear to be responsible for the observed mutants' activities. Nitrate reductase is proposed to be autoregulated. (iii) Mutants (am) lacking NADPH-dependent glutamate dehydrogenase activity partially escape ammonium repression of nitrate reductase. The presence of nitrate is required for the enzyme's induction. (iv) A double mutant, nit-1 am-2, proved to be an ideal test system to study the repressive effects of nitrogen-containing metabolites on the induction of nitrate reductase activity. The double mutant does not require nitrate for induction of nitrate reductase, and synthesis of the enzyme is not repressed by the presence of high concentrations of ammonium ions. It is, however, repressed by the presence of any one of six amino acids. Nitrogen metabolites (other than ammonium) appear to be responsible for the mediation of "ammonium repression."
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PMID:Induction and repression of nitrate reductase in Neurospora crassa. 14

A mutation leading to partial loss of NAD-linked ("catabolic') glutamate dehydrogenase does not affect the regulation of ammonium-repressible activities in Aspergillus nidulans. This mutation has been used to show that NAD-linked glutamate dehydrogenase does not normally participate in ammonium assimilation. A mutation leading to loss of NADP-linked ("anabolic') glutamate dehydrogenase has been used to show that NADP-linked glutamate dehydrogenase is not normally involved in glutamate catabolism. Strains defective in either enzyme are useful for determining which amino acids are metabolised via transamination to yield glutamate rather than via deamination to yield ammonium.
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PMID:A mutant of Aspergillus nidulans defective in NAD-linked glutamate dehydrogenase. 17 77

Metabolic effects of increased mechanical work were studied by comparing isolated pumping rat hearts perfused by the atrial-filling technique with aortic-perfused non-pumping hearts perfused by the technique of Langendorff. The initial medium usually contained glucose (11 mm) and palmitate (0.6 mm bound to 0.1 mm albumin). During increased heart work (comparing pumping with non-pumping hearts) the uptake of oxygen and glucose increased threefold, but that of free fatty acids was unchanged. Tissue contents of alpha-oxoglutarate, NH4+, malate, lactate, pyruvate and Pi rose with increased heart work, but contents of ATP, phosphocreatine and citrate fell. Ketone bodies were produced with a ratio of beta-hydroxybutyrate/acetoacetate of about 3:1 in both pumping and non-pumping hearts but with higher net production rates in non-pumping hearts. When ketone bodies were added in relatively high concentrations (total 4 mm) to a glucose (11 mm) medium the medium, ratios of beta-hydroxybutyrate/acetoacetate were not steady even after 60 min of perfusion. The validity of calculating mitochondrial free NAD+/NADH ratios from the tissue contents of the reactants of the glutamate dehydrogenase system or the beta-hydroxybutyrate dehydrogenase system is assessed. The activities of these enzymes are considerably less in the rat heart than in the rat liver, introducing reservations into the application to the heart of the principles used by Williamson et al. (1967) for calculation of mitochondrial free NAD+/NADH ratios of liver mitochondria...
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PMID:Effects of increased mechanical work by isolated perfused rat heart during production or uptake of ketone bodies. Assessment of mitochondrial oxidized to reduced free nicotinamide-adenine dinucleotide ratios and oxaloacetate concentrations. 17 81

Ten mutants of Aspergillus nidulans lacking nicotinamide adenine dinucleotide-specific glutamate dehydrogenase (NAD-GDH) have been isolated, and their mutations (gdhB1 through gdhB10) have been shown to lie in the gdhB gene. In addition, a temperature-sensitive gdhB mutant (gdhB11) has been isolated. A revertant (designated R-5) of the mutant gdhB1 bears an additional lesion in the gdhB gene and has altered NAD-GDH activity with altered Km values for ammonia or ammonium ions and for alpha-ketoglutarate. These results suggest that gdhB specifies a structural component for NAD-GDH. The growth characteristics of gdhB mutants indicate the routes by which amino acids are utilized as nitrogen and carbon energy sources. The properties are described of the double mutants bearing the mutations gdhB1 and gdhA1 or tamA119, which have low NADP-GDH activity.
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PMID:Mutants of Aspergillus nidulans lacking nicotinamide adenine dinucleotide-specific glutamate dehydrogenase. 17 7

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

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

Glutamate dehydrogenase from pig kidney has been purified to homogeneity by means of affinity chromatography on matrix bound Cibacron Blue F3G-A and gel chromatography on Sepharose 6B. The enzyme exhibits allosteric properties with the substrates alpha-ketoglutarate, ammonium, and NADH, respectively. GTP is a strong inhibitor which strengthened the cooperative interactions between the ammonium binding sites. ADP as an activator relieves the inhibition by GTP. Like glutamate dehydrogenase from bovine liver, glutamate dehydrogenase from pig kidney shows the ability of self-association, too. The sedimentation coefficient increases from 13.5 S at 0.07 mg protein/ml to 19.4 S at 1.32 mg protein/ml. In the sodium dodecylsulphate gel electrophoresis the enzyme migrates as a single band with a molecular-weight at 51000.
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PMID:Purification and properties of pig kidney glutamate dehydrogenase. 20 75

NAD-specific glutamate dehydrogenase (GDH-B) was induced in a wild-type strain derived of alpha-sigma 1278b by alpha-amino acids, the nitrogen of which according to known degradative pathways is transferred to 2-oxoglutarate. A recessive mutant (gdhB) devoid of GDH-B activity grew more slowly than the wild type if one of these amino acids was the sole source of nitrogen. Addition of ammonium chloride, glutamine, asparagine or serine to growth media with inducing alpha-amino acids as the main nitrogen source increased the growth rate of the gdhB mutant to the wild-type level and repressed GDH-B synthesis in the wild type. Arginine, urea and allantoin similarly increased the growth rate of the gdhB mutant and repressed GDH-B synthesis in the presence of glutamate, but not in the presence of aspartate, alanine or proline as the main nitrogen source. These observations are consistent with the view that GDH-B in vivo deaminates glutamate. Ammonium ions are required for the biosynthesis of glutamine, asparagine, arginine, histidine and purine and pyrimidine bases. Aspartate and alanine apparently are more potent inducers of GDH-B than glutamate. Anabolic NADP-specific glutamate dehydrogenase (GDH-A) can not fulfil the function of GDH-B in the gdhB mutant. This is concluded from the equal growth rates in glutamate, aspartate and proline media as observed with a gdhB mutant and with a gdhA, gdhB double mutant in which both glutamate dehydrogenases area lacking. The double mutant showed an anomalous growth behaviour, growth rates on several nitrogen sources being unexpectedly low.
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PMID:A mutant of Saccharomyces cerevisiae lacking catabolic NAD-specific glutamate dehydrogenase. Growth characteristics of the mutant and regulation of enzyme synthesis in the wild-type strain. 22 4


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