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)

The purification and some properties of NADP-dependent glutamate dehydrogenase (GDH) and glutamine synthetase (GS) from the facultatively anaerobic Gram-negative bacterium Paracoccus denitrificans were investigated. The enzymes were purified to homogeneity using a procedure which involved affinity chromatography on Blue Sepharose CL-6B as the major purification step. The recoveries in the purification of GDH and GS were 28% and 64%, respectively. The specific activity of purified GDH was 183 nkat (mg protein)-1 (deaminating reaction). GDH was composed of subunits of molecular mass 47 kDa and the native enzyme was either a tetramer or hexamer. The apparent Km values for L-glutamate, NADP, 2-oxoglutarate, NADPH and ammonia were 1.5 mM, 5.9 microM, 0.47 microM, 12.5 microM and 14 mM, respectively. The specific activity of purified GS was 1125 nkat (mg protein)-1 (transferase reaction). The molecular mass of native GS was 570 kDa; it was composed of 12 subunits of molecular mass 50.1 kDa. The apparent Km values for L-glutamine and hydroxylamine in the transferase reaction were 2.1 and 2.4 mM, respectively; those of ammonia, L-glutamate and ATP in the biosynthetic reaction were 0.03, 1 and 0.17 mM, respectively. After the adenylylation of GS, the Km for L-glutamine and L-glutamate increased and reached the values of 8.0 and 27 mM, respectively. The effects of the changes in GS activity on the ammonia metabolism of Paracoccus denitrificans are discussed.
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PMID:Purification and some properties of glutamate dehydrogenase and glutamine synthetase from Paracoccus denitrificans. 135 41

Pathophysiological concentrations of ammonia, both in vivo and in vitro, suppressed the production of 14CO2 from 14C-labelled glutamate and aspartate in astrocytes isolated from the rat cerebellum. Suppression of 14CO2 production with (aminooxy)acetic acid but not with glutamic acid diethyl ester indicated that transamination plays a major role in the oxidation of glutamate carbons. Activities of the enzymes, aspartate amino-transferase, alanine aminotransferase and glutaminase were decreased while those of glutamate dehydrogenase and glutamine synthetase were enhanced in the cerebellar astrocytes during hyperammonemic states. These results suggest an impairment of astrocytic glutamate metabolism during hyperammonemia.
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PMID:Hyperammonemic alterations in the metabolism of glutamate and aspartate in rat cerebellar astrocytes. 135 96

We examined freshly collected samples of the colonial planktonic cyanobacterium Trichodesmium thiebautii to determine the pathways of recently fixed N within and among trichomes. High concentrations of glutamate and glutamine were found in colonies. Glutamate and glutamine uptake rates and concentrations in cells were low in the early morning and increased in the late morning to reach maxima near midday; then uptake and concentration again fell to low values. This pattern followed that previously observed for T. thiebautii nitrogenase activity. Our results suggest that recently fixed nitrogen is incorporated into glutamine in the N2-fixing trichomes and may be passed as glutamate to non-N2-fixing trichomes. The high transport rates and concentrations of glutamate may explain the previously observed absence of appreciable uptake of NH4+, NO3-, or urea by Trichodesmium spp. Immunolocalization, Western blots (immunoblots), and enzymatic assays indicated that glutamine synthetase (GS) was present in all cells during both day and night. GS appeared to be primarily contained in cells of T. thiebautii rather than in associated bacteria or cyanobacteria. Double immunolabeling showed that cells with nitrogenase (Fe protein) contained levels of the GS protein that were twofold higher than those in cells with little or no nitrogenase. GS activity and the uptake of glutamine and glutamate dramatically decreased in the presence of the GS inhibitor methionine sulfoximine. Since no glutamate dehydrogenase activity was detected in this species, GS appears to be the primary enzyme responsible for NH3 incorporation.
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PMID:Glutamine synthetase and nitrogen cycling in colonies of the marine diazotrophic cyanobacteria Trichodesmium spp. 135 37

Characteristics of the three major ammonia assimilatory enzymes, glutamate dehydrogenase (GDH), glutamine synthetase (GS) and glutamate synthase (GO-GAT) in Corynebacterium callunae (NCIB 10338) were examined. The GDH of C. callunae specifically required NADPH and NADP+ as coenzymes in the amination and deamination reactions, respectively. This enzyme showed a marked specificity for alpha-ketoglutarate and glutamate as substrates. The optimum pH was 7.2 for NADPH-GDH activity (amination) and 9.0 for NADP(+)-GDH activity (deamination). The results showed that NADPH-GDH and NADP(+)-GDH activities were controlled primarily by product inhibition and that the feedback effectors alanine and valine played a minor role in the control of NADPH-GDH activity. The transferase activity of GS was dependent on Mn+2 while the biosynthetic activity of the enzyme was dependent on Mg2+ as essential activators. The pH optima for transferase and biosynthetic activities were 8.0 and 7.0, respectively. In the transfer reaction, the Km values were 15.2 mM for glutamine, 1.46 mM for hydroxylamine, 3.5 x 10(-3) mM for ADP and 1.03 mM for arsenate. Feedback inhibition by alanine, glycine and serine was also found to play an important role in controlling GS activity. In addition, the enzyme activity was sensitive to ATP. The transferase activity of the enzyme was responsive to ionic strength as well as the specific monovalent cation present. GOGAT of C. callunae utilized either NADPH or NADH as coenzymes, although the latter was less effective. The enzyme specifically required alpha-ketoglutarate and glutamine as substrates.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Some properties of glutamate dehydrogenase, glutamine synthetase and glutamate synthase from Corynebacterium callunae. 135 47

Corynebacterium callunae (NCIB 10338) grows faster on glutamate than ammonia when used as sole nitrogen sources. The levels of glutamine synthetase (GS; EC 6.3.1.2) and glutamate synthase (GOGAT; EC 1.4.1.13) of C. callunae were found to be influenced by the nitrogen source. Accordingly, the levels of GS and GOGAT activities were decreased markedly under conditions of ammonia excess and increased under low nitrogen conditions. In contrast, glutamate dehydrogenase (GDH; EC 1.4.1.4) activities were not significantly affected by the type or the concentration of the nitrogen source supplied. The carbon source in the growth medium could also affect GDH, GS and GOGAT levels. Of the carbon sources tested in the presence of 2 mM or 10 mM ammonium chloride as the nitrogen source pyruvate, acetate, fumarate and malate caused a decrease in the levels of all three enzymes as compared with glucose. GDH, GS and GOGAT levels were slightly influenced by aeration. Also, the enzyme levels varied with the growth phase. Methionine sulfoximine, an analogue of glutamine, markedly inhibited both the growth of C. callunae cells and the transferase activity of GS. The apparent Km values of GDH for ammonia and glutamate were 17.2 mM and 69.1 mM, respectively. In the NADPH-dependent reaction of GOGAT, the apparent Km values were 0.1 mM for alpha-ketoglutarate and 0.22 mM for glutamine.
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PMID:The effect of various culture conditions on the levels of ammonia assimilatory enzymes of Corynebacterium callunae. 135 48

Ammonia, lactate and glutamate levels and the activities of glutamine synthetase (GS), glutamate dehydrogenase (GDH), glutaminase (GLN), aspartate transaminase (AST), phosphofructokinase (PFK) and monoamine oxidase (MAO) were compared in the brain tissue of normal and P. yoelii infected mice. The brain lactate increased by 96% at peak parasitaemia. Cerebral ammonia also exhibited an increase in infected mice which was parasitaemia dependent, while glutamate remained almost unchanged. The brain glutamine synthetase registered an increase of 35% (P < 0.001) in post-mitochondrial fractions, this effect being perceptible even at low parasitaemia, but attained constancy at parasitaemia levels higher than 20%. The activity of monoamine oxidase and phosphofructokinase increased by 105% (P < 0.02) and 41% (P < 0.05) respectively while glutamate dehydrogenase decreased by 15% (P < 0.001). Glutaminase and aspartate transaminase were not significantly influenced by infection (tested only at high parasitaemia levels). It has been postulated that cerebral hypoxia and aberrations in ammonia metabolism may both contribute towards malaria induced cerebral complications.
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PMID:Cerebral ammonia levels and enzyme changes during Plasmodium yoelii infection in mice. 136 Oct 9

It was established that liver insufficiency the activity of hepatic glutamate dehydrogenase is markedly reduced that is, apparently, the main cause of hyperammonemia that accompanies hepatic encephalopathy. Here occurs a significant reduction of the processes of ammonia detoxication with formation of glutamine in the liver as evidenced by changes of the activity of glutamine synthetase. Administration parenterally of a preparation of nitrous feeding increases essentially ammonia detoxicating function of muscular tissue which supplements the detoxicating function of the liver.
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PMID:[The enzymatic activity of ammonia metabolism in the liver during the parenteral nitrogen feeding of animals with experimental liver failure]. 141 86

Studies on the levels of glutamate dehydrogenase (GDH), glutamine synthetase, and glutamate synthase were carried out as a function of temperature, nutritional conditions, and the morphological (yeast or mycelium) form of Benjaminiella poitrasii. Since both NAD- and NADP-dependent GDH activities were found in B. poitrasii, the quantitative relation between these two enzymes expressed as the NADP-GDH/NAD-GDH activity ratio (GDH ratio) was studied to evaluate its possible role in the morphogenesis. In the yeast-to-mycelium transition, a decrease in the GDH ratio occurred (between 1 and 2 h) and germ tube formation could be observed only at 3 h. Under similar sets of experimental conditions, exogenous addition 1.0 mM of alpha-ketoglutarate delayed germ tube emergence (4 h) compared with the control. On the other hand, in the presence of 1.0 mM glutamate an earlier onset of the germ tube formation was noted. The morphological (monomorphic) mutants, Y-2 and Y-5, showed a high GDH ratio and maintained the yeast morphology.
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PMID:Significance of NADP/NAD glutamate dehydrogenase ratio in the dimorphic behavior of Benjaminiella poitrasii and its morphological mutants. 159 24

Injection with pharmacological doses of dexamethasone (5 mg/kg) and/or bovine glucagon (1 mg/kg) exerts pronounced effects on toadfish liver compared with vehicle-treated control fish. Affected parameters include hepatic levels of glycogen and the activities of glutamate dehydrogenase, aspartate aminotransferase, malate dehydrogenase, and enzymes involved in NADPH generation as well as the kinetics of pyruvate kinase. Activities of tyrosine aminotransferase, however, a prime target for hormonal induction in mammals, remain unchanged in Opsanus. In subsequently isolated toadfish hepatocytes, metabolite concentrations and flux through gluconeogenesis are altered as are in vitro responses to epinephrine and catfish glucagon in previously injected fish. Contrary to existing mammalian models, short-term regulation of urea cycle activity can be ruled out for toadfish, since hormone treatments fail to influence the activity of two ornithine-urea cycle enzymes or the rate of hepatocyte-urea synthesis. Treatment-dependent increases in hepatic glutamine synthetase, the unique feeder enzyme for ammonia "nitrogen" in fish urea cycle, indicate a potentially pivotal role for this enzyme in longer-term regulation of ureogenesis.
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PMID:Metabolic actions of glucagon and dexamethasone in liver of the ureogenic teleost Opsanus beta. 160 Dec 63

Amino acid metabolism was examined in mitochondria from the lateral red muscle of a teleost (lake char, Salvelinus namaycush) and a nonteleost fish (bowfin, Amia calva). Isolated mitochondria oxidize a wide variety of substrates and have high respiratory control ratios. In both species, glutamine is oxidized more rapidly than any other amino acid. The rate of glutamine oxidation by bowfin mitochondria exceeds that of lake char mitochondria, and the bowfin displays correspondingly higher levels of mitochondrial phosphate-dependent glutaminase. It is suggested that amino acids in general, and glutamine in particular, are important oxidative substrates for nonteleost red muscle. The teleost red muscle, however, may rely on both glutamine and fatty acids as oxidative substrates. It appears that glutamate derived from glutamine is oxidized primarily via glutamate dehydrogenase, whereas exogenous glutamate is oxidized primarily via aspartate aminotransferase. Complete oxidation of glutamine may be accomplished in the absence of other substrates by conversion of glutamine-derived malate to pyruvate via malic enzyme. To assess the relative abilities of various tissues to synthesize and oxidize glutamine, the activities of glutamine synthetase and glutaminase were measured. The results of these studies indicate that the organization of glutamine metabolism of fish differs markedly from that in mammals.
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PMID:Glutamine metabolism in a holostean (Amia calva) and teleost fish (Salvelinus namaycush). 167 42


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