Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.4.1.4 (glutamate dehydrogenase)
 4,358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The reactive analogue oADP produced by periodate oxidation of ADP has been studied as a potential affinity label for the enzyme bovine glutamate dehydrogenase, using circular dichroism (CD) difference spectroscopy to monitor specific binding. 2. The analogue binds stoichiometrically, rapidly and reversibly to the adenine nucleotide binding site with Kd approximately equal to 12 microM (20 degrees C, pH 7) with characteristic intensification of the adenine nucleotide CD at 260 nm. 3. This complex is unstable and decays with a half-life of about 1.5 h; the analogue then becomes attached as a Schiff base to a number of subsidiary sites, including the enzyme active site, with partial inactivation of the enzyme. 4. Depending upon initial concentration of oADP, the enzyme activity is progressively lost during the slow reaction; following borohydride reduction, up to four molecules of analogue are bound/subunit. 5. Protection against loss of enzyme activity is afforded by the coenzyme NAD+ plus glutarate or L-hydroxyglutarate (an effective inhibitor), or by glutarate alone, but not by NAD+ alone. 6. Spectroscopic and protection studies indicate that after the decay of the specific CD signal, the enzyme retains the capacity to bind ADP, but that this is progressively lost in parallel with decay of enzymic activity. 7. The results are consistent with proximity or functional interaction between the adenine nucleotide site and the coenzyme binding portion of the active site. 8. Thus oADP does not act as a true affinity label for the adenine nucleotide binding site, but the reaction subsequent to binding at that site shows some specificity directed towards the active site.
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PMID:The reaction of bovine glutamate dehydrogenase with periodate-oxidised ADP. 628 11

The activity of certain key enzymes involved in glutamic acid metabolism was studied in purified brain mitochondria and in mitochondrial subfractions separated in a discontinuous 1.2--1.6 mol/l sucrose gradient. Alanine aminotransferase and glutamate dehydrogenase were found to be matrix enzymes and aspartate aminotransferase to be associated with the inner mitochondrial membranes. After the purified mitochondria had been separated into 5 subfractions, aspartate aminotransferase and NAD+-dependent isocitrate dehydrogenase were found to be bound to the lighter mitochondrial subfractions settling at the 1.4--1.5 mol/l sucrose boundary while alanine aminotransferase, 4-aminobutyrate transaminase and glutamate dehydrogenase were associated with the heavier subfractions settling below 2.4 mol/l sucrose. The highest specific activity of the given enzymes was found in the subfraction settling at the 1.4--1.5 mol/l sucrose boundary, the only exception being alanine aminotransferase activity, whose maximum was found in the subfractions settling in 1.5 and 1.6 mol/l sucrose. It was concluded that alanine aminotransferase, in conjunction with glutamate dehydrogenase, is linked to NH3 binding and to the oxidation of reduced adenine nucleotides; in addition, alanine aminotransferase is presumed to have the function of transporting glutamate from the mitochondria to the extramitochondrial space.
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PMID:Alanine aminotransferase and some other enzymes in different populations of free brain cortex mitochondria. 645 52

The effects of ATP and GTP on the activities of ox liver and brain glutamate dehydrogenase were determined in the absence and presence of added Mg2+ ions. Although GTP was an inhibitor of the enzyme reaction assayed in the direction of NAD+ reduction, the magnesium complex of this nucleotide had no effect on the activity. Similarly the magnesium complex of ATP was without effect on the activity of the enzyme although the free nucleotide was an activator. These results suggest that it is important to take account of magnesium complex formation when considering the regulatory actions of these nucleotides.
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PMID:The effects of magnesium ions on the interactions of ox brain and liver glutamate dehydrogenase with ATP and GTP. 646 7

(2S,4R)-"erythro"- and (2S,4S)-"threo"-4-methylglutamic acids have been prepared by glutamate dehydrogenase-catalyzed reductive amination of 2-keto-(R,S)-4-methylglutaric acid, in the presence of NH4+ ions, NAD+, and a NADH recycling system (ethanol-alcohol dehydrogenase), followed by separation by anion-exchange chromatography. Nuclear magnetic resonance, electrophoretic, chromatographic, and optical properties of both isomers are reported, together with the conditions leading to the four-carbon epimerization.
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PMID:An enzymatic synthesis of 4-methyl-L-glutamic acid diastereoisomers. 653 47

The amino acid sequence of the NADP+-dependent enzyme ovine 6-phosphogluconate dehydrogenase has been determined by conventional direct protein sequence analysis of peptides resulting from digestion of the protein with trypsin and chemical cleavages with cyanogen bromide, hydroxylamine, and iodosobenzoic acid. The polypeptide contains 466 amino acids and its NH2 terminus is acetylated. The Candida utilis enzyme is inactivated by reaction of pyridoxal phosphate with two lysine residues (Minchiotti, L., Ronchi, S., and Rippa, M. (1981) Biochim. Biophys. Acta 657, 232-242). These residues are conserved in the ovine enzyme. In contrast to NAD+ dehydrogenases which have weakly related sequences and spatially related folds in their nucleotide-binding sites, no significant sequence homologies were detected between 6-phosphogluconate dehydrogenase and any of three other NADP+-requiring enzymes, glutamate dehydrogenase, p-hydroxybenzoate hydroxylase, and dihydrofolate reductase. This is in accord with structural data that show no spatial relationship between NADP+-binding sites in these enzymes.
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PMID:Amino acid sequence of ovine 6-phosphogluconate dehydrogenase. 668 25

1. A simple, facile one-step method has been devised to measure the stereospecificity of NADP+-linked oxidoreductases. The procedure involves coupling the test enzymes to enzymes of known stereospecificity in the presence of deuterated substrates. The regenerated NADP+ in the coupled reactions is analyzed by PMR for its deuterium content at the carbon-4 position of the nicotinamide ring. 2. It is found that malate dehydrogenase (EC 1.1.1.37), lactate dehydrogenase (EC 1.1.1.27) and glycerate dehydrogenase (EC 1.1.1.29) are A-side stereospecific whereas glutamate dehydrogenase (EC 1.4.1.3) and glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) are B-side stereospecific. 3. Enzymes which can utilize both NAD+ and NADP+ have the same stereospecificity with respect to the coenzyme.
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PMID:A one-step PMR determination of hydrogen transfer stereospecificity of NADP+-linked oxidoreductases. 682 14

The kinetic mechanism of glutamate dehydrogenase with the monocarboxylic substrate norvaline was examined by using initial-rate steady-state kinetics and inhibition kinetics. To a first approximation the reaction mechanism can be described as a rapid-equilibrium random-order one. Binding synergism between the monocarboxylic substrate and coenzyme is not observed. Dissociation constants for NAD+ and 2-oxoglutarate calculated from the kinetic data assuming a rapid-equilibrium random-order model are in good agreement with independently obtained estimates. Lineweaver-Burk plots with varied norvaline concentration are not strictly linear, and it is concluded that a steady-state random-order model more accurately reflects the observed kinetics with norvaline as substrate.
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PMID:A steady-state random-order mechanism for the oxidative deamination of norvaline by glutamate dehydrogenase. 687 Aug 33

Transferred nuclear Overhauser enhancement was used to examine the conformation of NAD+ and NADP+ bound to glucose-6-phosphate dehydrogenase and glutamate dehydrogenase and of NAD+ bound to lactate dehydrogenase. The results demonstrate that the conformation of the nicotinamide-ribose bond is anti for dehydrogenases with A stereospecificity and syn for dehydrogenases with B stereospecificity. In those dehydrogenases that bind both NAD+ and NADP+, significant differences occur in the conformations of the bound nicotinamide coenzymes.
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PMID:Conformations of nicotinamide coenzymes bound to dehydrogenases determined by transferred nuclear Overhauser effects. 687 Nov 63

Hysteresis in glutamate dehydrogenase is observed only in the reductive amination reaction and only with GTP present. The rate of reductive amination with NADH as coenzyme increases during the time course of the reaction. Premixing experiments, where glutamate dehydrogenase is preincubated with various combinations of substrates and GTP, suggest that the hysteresis phenomenon is not due to a time-dependent conformational change in the enzyme. Enzyme dilution experiments show (i) that the hysteresis is not due to enzyme association-dissociation effects and (ii) that the onset of the activation occurs after accumulation of about 25 microM NAD+. Addition of NAD+ to the initial reaction mixture prevents hysteresis from occurring. Although with NADPH as coenzyme hysteresis does not occur, addition of NADP+ to initial reaction mixtures containing NADH blocks hysteresis. A model based on reciprocating subunits is proposed whereby hysteresis results from product (NAD+) accumulation resulting in a half-of-the-sites activation of reductive amination.
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PMID:Mechanism of hysteresis in bovine glutamate dehydrogenase: role of subunit interactions. 707 37

This study is an investigation into the validity of calculating the mitochondrial redox state in brain in vivo using models of seizure and anoxia in rats. At six intervals following electroconvulsive seizure (0.5-10 min) and after 5 min of complete anoxia, multiple metabolites were measured in freeze-blown or freeze-clamped brain. From substrate ratios, the apparent changes in the mitochondrial free [NAD+]/[NADH] [H+] ratio were calculated from the L-glutamate dehydrogenase reaction [EC 1.4.1.3] and compared with shifts in the oxidized to reduced ratio of total ubiquinone (a component of the mitochondrial phosphorylation chain). During complete anoxia the calculated mitochondrial free [NAD+]/[NADH] [H+] ratio and the ubiquinone redox ratio both became more reduced by a factor of approximately 7. In contrast, following seizure the two indicators of the mitochondrial redox state moved in opposite directions. Mainly because of a large increase in tissue NH4+, the calculated mitochondrial free [NAD+]/[NADH] [H+] ratio paradoxically became more oxidized, plateauing between 2 and 10 min post seizure at a value approximately double that of the control. At the same time, however, the ubiquinone redox state fell to one-half the control value at two min and moved back towards normal between 5 and 10 min after the onset of the seizure. The results have been taken to be evidence against the applicability of the calculation of the mitochondrial free [NAD+]/[NADH] [H+] ratio from the L-glutamate dehydrogenase reaction in brain at least under conditions of rapid change. The results also suggest the possibility that the NH4+ produced during seizure is extra-mitochondrial and has relatively little tendency to diffuse into the matrix.
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PMID:The calculation of the mitochondrial free [NAD+]/[NADH][H+] ratio in brain: effect of electroconvulsive seizure. 709 92


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