Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.4.1.2 (glutamate dehydrogenase)
 4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A spin-labelled analogue of p-chloromercuribenzoate reacts specifically with glutamate dehydrogenase. The most marked change in the properties of the spin-labelled enzyme is a fivefold decrease in the rate of reduction of the coenzyme by L-glutamate and no change in the rate of oxidation by 2-oxoglutarate. The electron spin resonance spectrum is a sensitive probe for the conformational state of the enzyme. Spin-labelled glutamate dehydrogenase in the presence of saturating concentrations of NADPH and 2-oxoglutarate or L-glutamate shows a complete conformational change while in the presence of NADP+ and 2-oxoglutarate only half of the protomers have changed conformation. The conformational change upon addition of NADPH to the spin-labelled glutamate dehydrogenase in the presence of 2-oxoglutarate happens in a concerted way between 20 and 80% saturation with NADPH. One of the conformations is favoured by the activator ADP while the other is favoured by the inhibitor GTP.
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PMID:Conformational changes in bovine-liver glutamate dehydrogenase: a spin-label study. 3 11

ADP and ATP with a spin-label linked to the terminal phosphate are activators of glutamate dehydrogenase and bind to the same site as the activator ADP. There is hardly any interaction with the coenzyme site. Glutamate dehydrogenase can be modified with a ketone spin-label at a site in the active centre[Andree and Zantema, (1978) Biochemistry, 17, 778--783]. The spin-labelled activators interact with ketone spin-labelled glutamate dehydrogenase in the same way as with native glutamate dehydrogenase relative to the activator site, but show a stronger binding to the coenzyme site. Upon binding to the coenzyme site a spin-spin interaction between the ketone spin-label and the spin-labelled activators is observed. Nuclear magnetic resonance studies of the linewidth of 2-oxoglutarate and NADP+ bound to their functional sites on glutamate dehydrogenase without and with spin-labels result in distances between the ligand nuclei and the spin-labels. The results show that NADP+ binds in an open conformation consistent with the conformation in other dehydrogenases. The activator ADP binds in the neighbourhood of the active centre, but with very little or no overlap with the coenzyme site.
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PMID:Magnetic-resonance studies of the geometry of bound substrate, coenzyme and activator on bovine-liver glutamate dehydrogenase. 3 12

The contributions of NAD-specific and NADP-specific isocitrate dehydrogenases to isocitrate oxidation in isolated intact rat liver mitochondria were examined using DL-threo-alpha-methylisocitrate (3-hydroxy-1,2,3-butanetricarboxylate) to specifically inhibit flux through NADP-specific isocitrate dehydrogenase. Under a range of conditions tested with respiring mitochondria, the rate of isocitrate oxidation was decreased by about 20--40% by inhibition of NADP-isocitrate dehydrogenase, and matrix NADP became more oxidized. (a) For mitochondria incubated with externally added DL-isocitrate and citrate, the rate of isocitrate oxidation obtained by extrapolation to infinite alpha-methylisocitrate concentration was approximately 70% of the uninhibited rate in both state 3 and state 4. (b) With pyruvate plus malate added as substrates of citric acid cycle oxidation and isocitrate generated intramitochondrially, a concentration of alpha-methylisocitrate (400 microM) sufficient for 99.99% inhibition of NADP-isocitrate dehydrogenase inhibited isocitrate oxidation in states 4 and 3 by 21 +/- 6% and 19 +/- 11% (mean +/- SEM), respectively. (c) With externally added isocitrate and citrate, the addition of NH4Cl increased isocitrate oxidation by 3--4-fold, decreased NADPH levels by 30--40% and 2-oxoglutarate accumulation by about 40%. The further addition of 600 microM alpha-methylisocitrate decreased the NH4Cl-stimulated isocitrate oxidation by about 40% and decreased NADPH to about 30% of the level prevailing in the absence of NH4Cl; nevertheless, the rate of isocitrate oxidation was still twice as large in the presence of NH4Cl and alpha-methylisocitrate as in their absence. Experiments were also performed with intact mitochondria incubated with respiratory inhibitors to determine additional factors which might affect the flux through the two isocitrate dehydrogenases. (a) In the coupled reduction of acetoacetate by isocitrate, where the rate of reoxidation of reduced pyridine nucleotides is limited by NAD-specific 3-hydroxybutyrate dehydrogenase, 85--100% of the rate of 3-hydroxybutyrate formation was retained in the presence of 400--900 microM alpha-methylisocitrate. (b) In a system where the rate of isocitrate oxidation is limited by the rate of NADPH reoxidation by glutathione reductase, the rate of glutathione reduction extrapolated to infinite alpha-methylisocitrate concentration was from 20--40% of the uninhibited rate. (c) In the coupled synthesis of glutamate from isocitrate and NH4Cl, where the reoxidation of NADPH and NADH can occur via glutamate dehydrogenase, the rate of glutamate production extrapolated to infinite alpha-methylisocitrate concentration was about 60% of the uninhibited rate.
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PMID:Activities of NAD-specific and NADP-specific isocitrate dehydrogenases in rat-liver mitochondria. Studies with D-threo-alpha-methylisocitrate. 3 61

The purified NADP-linked glutamate dehydrogenase from Trypanosoma cruzi was strongly inhibited by silver nitrate. The inhibition was reversed by reduced glutathione, and was modified by the presence of the substrates during preincubation of the enzyme with the inhibitor.
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PMID:Inhibition of the NADP-linked glutamate dehydrogenase from Trypanosoma cruzi by silver nitrate. 3 72

The present report concerns the study of the catalytic properties and the coenzyme affinity of glutamate dehydrogenase (GDH) and its isoenzymes in various preparations of the brain and liver as well as the different regulatory mechanisms controlling the ratio of the rates of biogenesis and breakdown of glutamate (Glu). The investigations carried out showed that GDH activity of various preparations of brain and liver (crystalline enzymes, cellular extracts and mitochondria) are markedly different from each other by their catalytic and regulatory properties as well as by their coenzyme activity. The data obtained make us conclude that nicotinamide-hypoxanthine-nucleotide (deaminoNAD) is a more effective coenzyme in the oxidative deamination of Glu, than other piridine nucleotides (NAD, NADP, deamino-NADP). It is supposed that in the formation of ammonia and amino acids in brain and especially liver, together with other known mechanisms an important role may be ascribed to the process of transdeamination. In this aspect, as a co-factor of oxidative deamination of Glu deamino-NAD (D-NAD) is thought to be of significant importance.
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PMID:[Heterogeneity and regulation of glutamate dehydrogenase activity in mammalian brain and liver]. 4 64

The glutamate dehydrogenase and glutamine synthetase activities of an obligate halophyte, Suaeda maritima var. macrocarpa and a glycophyte. Phaseolus vulgaris are compared in function of salinity (increasing concentrations of NaCl) of the culturing solution. In culture, addition of NaCl stimulates glutamine synthetase activity and lowers glutamine dehydrogenase activity in the aerial organs and in the roots of Suaeda as opposed to what is observed in the glycophyte. Hence the obligatory halophily of Suaeda is related to an increase of the glutamine synthetase activity in a sal-trich medium corresponding to the stimulation of nitrate reductase and proteogenesis.
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PMID:[Comparison of glutamate dehydrogenase and glutamine synthetase activities in the roots and aerial organs of an obligate halophyte: Suaeda maritima var. macrocarpa and a glycophyte: Phaseolus vulgaris, grown in presence of different concentration of NaCl]. 4 95

1. Radioactively labelled 4-methyl-2-oxopentanoate was taken up by isolated pancreatic islets in a concentration- and pH-dependent manner and led to the intracellular accumulation of labelled amino acid and to a decrease in the intracellular pH. Uptake of 4-methyl-2-oxopentanoate did not appear to be either electrogenic or Na+-dependent. The islet content of 2-oxo acid radioactivity was not affected by either 2-cyano-3-hydroxy-cinnamate (10mM) or pyruvate (10mM), although both these substances inhibited the oxidation of [U-14C]4-methyl-2-oxopentanoate by islet tissue. 2. 4-Methyl-2-oxopentanoate markedly stimulated islet-cell respiration, ketone-body formation and biosynthetic activity. The metabolism of endogenous nutrients by islets appeared to be little affected by the compound. 3. Studies with the 3H- and 14C-labelled substrate revealed that 4-methyl-2-oxopentanoate was incorporated by islets into CO2, water, acetoacetate, L-leucine and to a lesser extent into islet protein and lipid. Carbon atoms C-2, C-3 and C-4 of the acetoacetate produced were derived from the carbon skeleton of the 4-methyl-2-oxopentanoate, but the acetoacetate carboxy group was derived from the incorporation of CO2. These results, and consideration of the relative rates of 14CO2 and acetoacetate formation from 1-14C-labelled as opposed to U-14C-labelled 4-methyl-2-oxopentanoate, led to the conclusion that the pathway of catabolism of this 2-oxo acid in pancreatic islets is identical with that described in other tissues. The amination of 4-methyl-2-oxopentanoate by islets was attributed to the presence of a branched-chain amino acid aminotransferase (EC 2.6.1.42) activity in the tissue. Although glutamate dehydrogenase activity was demonstrated in islet tissue, the reductive amination of 2-oxoacids did not seem to be of importance in the formation of leucine from 4-methyl-2-oxopentanoate. 4. The results of experiments with respiratory inhibitors and uncouplers, and the finding that 14CO2 production and islet respiration were linked in a 1:1 stoicheiometry suggested that 4-methyl-2-oxopentanoate catabolism was coupled to mitochondrial oxidative phosphorylation. The catabolism of 4-methyl-2-oxopentanoate in islet tissue appeared to be regulated at the level of the initial 2-oxo acid dehydrogenase (EC 1.2.1.25) reaction.
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PMID:The metabolism of 4-methyl-2-oxopentanoate in rat pancreatic islets. 4 43

Biotin deficiency in Aspergillus nidulans resulted in a 70% increase of the protein content and increased levels of free and bound aspartate, glutamate, serine, leucine and methionine. Likewise, the activities of NADP+ glutamate dehydrogenase, NAD+ gluatmate dehydrogenase, aspartate aminotransferase and alanine aminotransferase were significantly increased. The total RNA content increased while the DNA content was unaffected. The rRNA/tRNA ratio remained higher in biotin-deficient cells. Supplementation of glutamate, aspartate, serine, leucine and methionine to the culture medium raised the rRNA/tRNA ratio, and the difference observed in the qualitative and the quantitative patterns of protein and dry cell mass between normal and biotin-deficient cultures was abolished.
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PMID:Factors affecting protein synthesis during biotin deficiency in Aspergillus nidulans. 4 77

In Saccharomyces cerevisiae, the presence or absence of NADP-specific glutamate dehydrogenase does not affect inhibition of sporulation by ammonia, suggesting that the inhibition is not mediated by this enzyme.
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PMID:NADP-specific glutamate dehydrogenase is not involved in repression of yeast sporulation by ammonia. 4 57

Earlier studies indicated that the gene of an ammonium-inducible glutamate dehydrogenase (GDH) was inducible throughout the cell cycle and was expressible shortly after replication early in the S-phase in synchronous Chlorella cells growing at a rate of 13% per h in the absence of inducer. In the present study, synchronous cells cultured at the same growth rate in the continuous presence of inducer accumulated this enzyme in a linear manner, with a positive rate change observed late instead of early in the S-phase. At a growth rate of 26% per h, the positive rate change appeared to be displaced to 1.5 h before the S-phase in the next cell cycle. With 2'-deoxyadenosine, an in vivo inhibitor of deoxyribonucleic acid (DNA) synthesis, the magnitude of the positive rate change was shown to be proportional to the relative increase in DNA in the previous cell cycle. Collectively, these data support the idea that expression of newly replicated genes of this enzyme can be delayed into the subsequent cell cycle in cells in the continuous presence of inducer. Studies with cycloheximide indicated that the inducible GDH and another GDH isozyme were stable in fully induced cells in the absence of protein synthesis. However, after ammonium was removed from the culture medium, the activity of the inducible GDH decreased rapidly in vivo, with a half-time of 5 to 10 min at 38.5 degrees C, whereas the rate of accumulation of the other GDH isozyme did not change. Addition of cycloheximide, at the time of inducer removal, prevented this loss in activity of the inducible GDH. The inability to rescue the activity of the inducible GDH, by readdition of ammonium during the deinduction period, indicates that this enzyme probably underwent irreversible inactivation and/or proteolytic degradation.
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PMID:Regulation of accumulation and turnover of an inducible glutamate dehydrogenase in synchronous cultures of Chlorella. 4 86


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