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)

Glutamate synthase was purified about 250-fold from Thiobacillus thioparus and was characterized. The molecular weight was estimated as 280,000 g/mol. The enzyme showed absorption maxima at 280, 380, and 450 nm and was inhibited by Atebrin, suggesting that T. thioparus glutamate synthase is a flavoprotein. The enzyme activity was also inhibited by iron chelators and thiolbinding agents. The enzyme was specific for reduced nicotinamide adenine dinucleotide phosphate (NADPH) and alpha-ketoglutarate, but L-glutamine was partially replaced by ammonia as the amino donor. The Km values of glutamate synthase for NADPH, alpha-ketoglutarate, and glutamine were 3.0 muM, 50 muM, and 1.1 mM, respectively. The enzyme had a pH optimum between 7.3 and 7.8. Glutamate synthase from T. thioparus was relatively insensitive to feedback inhibition by single amino acids but was sensitive to the combined effects of several amino acids. Enzymes involved in glutamate synthesis in T. thioparus were studied. Glutamine synthetase and glutamate synthase, as well as two glutamate dehydrogenases (NADH and NADPH dependent), were present in this organism. This levels of glutamate synthase and glutamate dehydrogenase were similar in T. thioparus grown on 0.7 or 7.0 mM ammonium sulfate. The sum of the activities of both glutamate dehydrogenases was only 1/25 of that of glutamate synthase under the assay conditions. It was concluded that the glutamine pathway is important for ammonia assimilation in this autotrophic bacterium.
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PMID:Purification and properties of glutamate synthase from Thiobacillus thioparus. 1 19

In a detailed study focused on the methodological problems in dehydrogenase histochemistry [e.g., fixation, diffusion of enzymes and of reduced inermediates, conversion of NADPH and NADP to NADH and NAD, respectively, penetration of tetrazolium salt and formazan substantivity, 'nothing dehydrogenase' reaction, use of exogenous CoQ10 and of flavoprotein substitute (PMS)], the distribution and activity of succinate dehydrogenase, NAD(P)H-tetrazolium reductase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase (H and M types), and of L-glutamate dehydrogenase (E.C.1.4.1.2 and E.C.1.4.1.3) have been investigated in the rat cerebellum. It was evident from the study that reliable results could only be obtained if all the aforementioned factors had been considered. The image of actual concentration of SDH in the neuropil of the molecular layer could only be recorded by adding CoQ10, while other structures exhibited greater balance between SDH and endogenous mitochondrial CoQ. Contrary to previous studies, a reversed localization of the activity of G-6-PDH and LDH was noticed. The elements of molecular and Purkinje layers were rich in G-6-PDH, while the granular layer was nearly depleted. The actual level of LDH could only be recorded if NADH-tetrazolium reductase was bypassed with PMS. The H and M types of LDH coexisted in the three cortical layers, the H type being prevalent and the M type attaining its highest level in synaptic glomeruli followed by the structures of the molecular layer and the Purkinje cells. High activity of GDH was noticed in Bergmann glia followed by synaptic glomeruli, while most other structures showed weak to moderate activity. The two GDH types coexisted in all structures showing activity, except for Bergmann cells, which only showed presence of the E.C. 1.4.1.3 type. Furthermore, Bergmann glia was exceptional by showing no activity of SDH and LDH, but strong activity of G-6-PDH and NADPH-tetrazolium reductase. The granular cells were exceptional by showing weak or no activity of all enzymes in question.
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PMID:Methodological aspects of the histochemical localization and activity of some cerebellar dehydrogenases. 66 87

Reduced pyridine nucleotide dependent glutamate synthase [L-glutamate: NADP+ oxidoreductase (transaminating); EC 1.4.1.13] was purified to homogeneity from Bacillus subtilis PCI 219. The molecular weight of the enzyme was 210,000, and the enzyme was composed of two nonidentical subunits with molecular weights of 160,000 and 56,000. The absorption and CD spectra of the enzyme indicated that the enzyme is an iron-sulfur flavoprotein. The enzyme was found to contain 1:1:7.4:8.7 mol of FMN, FAD, iron atoms, and acid-labile sulfur atoms per mol (MW 210,000). EPR measurements of the NADPH-reduced enzyme at 77K revealed the formation of a stable flavin semiquinone intermediate; however, none of the signals originating from the iron-sulfur cluster was observed. Still at 4.2K the EPR signals in the region of g = 2, which may originate from the paramagnetic iron-sulfur cluster, were clearly observed for both the isolated and dithionite-reduced states of the enzyme. The enzyme exhibited a wide coenzyme specificity, and either NADPH or NADH could be used as electron donor, although the latter was less effective. The enzyme activity was also expressed when ammonium chloride was substituted for L-glutamine. The optimum pHs for NADPH-Gln-, NADH-Gln-, and NADPH-NH3-dependent reactions were 7.8, 6.9, and 9.4, respectively. The apoenzyme exhibited substantial inactivation of the Gln-dependent activities but still retained the NH3-dependent activities. Enzyme reduction-oxidation experiments, initial velocity experiments, and product inhibition patterns revealed that both the NADPH-Gln- and NADH-Gln-dependent reactions coincided with the two-site ping-pong uni-uni bi-bi kinetic mechanism, while the NADPH-NH3-dependent reaction deviated from Michaelis-Menten kinetics. The Gln-dependent activities were inhibited by several TCA cycle members, especially L-malate and fumarate, as well as L-methionine-SR-sulfoximine, pyridoxal-5'-phosphate, and pCMB. The regulation of the glutamate synthase, glutamine synthetase [EC 6.3.1.2], and glutamate dehydrogenase [EC 1.4.1.3] activities was examined with cultures of cells grown with various nitrogen and carbon sources.
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PMID:Glutamate synthase from Bacillus subtilis PCI 219. 301 66

The effects of gossypol, a polyphenolic compound isolated from the cotton plant upon six oxidoreductases from cultured epimastigotes of Typanosoma cruzi were studied. Gossypol was a powerful inhibitor of the alpha-hydroxyacid and malate dehydrogenases, NAD-linked enzymes, and of glutamate dehydrogenase, malic enzyme and glucose-6-phosphate dehydrogenase, NADP-dependent enzymes. The drug did not have an effect on succinate dehydrogenase, a flavoprotein. The Ki values with respect to substrate were 0.73, 0.3 and 3.5 microM for alpha-hydroxyacid, malate and glutamate dehydrogenases, respectively, and 1.1, 0.19 and 7.8 microM with respect to the coenzyme. Inhibition was noncompetitive with respect to substrate and uncompetitive in relation to the coenzyme.
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PMID:Inhibition by gossypol of oxidoreductases from Trypanosoma cruzi. 637 Feb 65

Glutamate synthase is a complex iron-sulfur flavoprotein containing one molecule each of FAD and FMN and three distinct iron-sulfur centers/alpha beta protomer. Production of the beta subunit was observed in total extracts of Escherichia coli BL21 (DE) cells harbouring a pT7-7 derivative carrying gltD, the gene encoding the Azospirillum brasilense glutamate synthase beta subunit. The protein was soluble, and the identity of the purified protein with the Azospirillum glutamate synthase beta subunit was confirmed by N-terminal sequence analysis. The kinetic and spectroscopic characterization of the glutamate synthase beta subunit confirmed that it contains the NADPH binding site, but, in contrast with earlier proposals that assigned both FAD and FMN binding sites to the alpha subunit of glutamate synthase, the beta subunit was shown to contain stoichiometric amounts of FAD. No iron-sulfur centers were detected by EPR spectroscopy measurements of the recombinant beta subunit. Under steady-state conditions, the glutamate synthase beta subunit can catalyze the NADPH-dependent reduction of several synthetic electron acceptors but no glutamate synthase or glutamate dehydrogenase reactions in either direction. The results are in agreement with previous data from our laboratory and, together with the absence of amino acid sequence similarity between glutamate synthase beta subunit and glutamate dehydrogenases, are against the hypothesis that glutamate synthase is evolutionarily derived from the association of an ancestral glutamate dehydrogenase (the beta subunit) and an amidotransferase (the alpha subunit). The protein-bound FAD is reduced by NADPH at a rate much faster than turnover with synthetic electron acceptors, leading to formation of a stable reduced flavin-NADP+ charge-transfer complex. The rate of reduction of the bound FAD by NADPH is also similar to the rate at which one of the flavins is reduced in the native glutamate synthase, as measured in a stopped-flow spectrophotometer under pre-steady-state conditions. The ability of FAD bound to the beta subunit of glutamate synthase to react with NADPH and the lack of reactivity with sulfite lead us to conclude that FAD is Flavin 1 of glutamate synthase [Vanoni, M.A., Edmondson, D.E., Zanetti, G. & Curti, B. (1992) Biochemistry 31, 4613-4623].
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PMID:Properties of the recombinant beta subunit of glutamate synthase. 866 16

A growing body of evidence has focused on the impact of mitochondrial disturbances in the development of depression, but little data exist regarding the effects of chronic administration of antidepressant drugs on the brain's mitochondrial protein profile. The aim of this study was to investigate the impact of chronic treatment with an atypical antidepressant drug-tianeptine-on the mitochondria-enriched subproteome profile in the hippocampus and the frontal cortex of 3-month-old male rats following a prenatal stress procedure. Rats that were exposed to a prenatal stress procedure displayed depressive- and anxiety-like disturbances based on the elevated plus-maze and Porsolt tests. Moreover, two-dimensional electrophoresis coupled with mass spectrometry showed structure-dependent mitoproteome changes in brains of prenatally stressed rats after chronic tianeptine administration. A component of 2-oxoglutarate and succinate flavoprotein subunit dehydrogenases, isocitrate subunit alpha, was upregulated in the hippocampus. In the frontal cortex, there was a striking increase in the expression of glutamate dehydrogenase and cytochrome bc1 complex subunit 2. These findings suggest that mitochondria are underappreciated targets for therapeutic interventions, and mitochondrial function may be crucial for the effective treatment of stress-related diseases.
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PMID:The effect of chronic tianeptine administration on the brain mitochondria: direct links with an animal model of depression. 2693 88