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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)

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

A simple, convenient, and rapid method for determining ammonia in plasma by the glutamate dehydrogenase reaction is described for the centrifugal analyzer. The measuring principle is fixed-time, with NADH as the coenzyme. ADP is added to stabilize glutamate dehydrogenase and prevent interference from endogenous plasma ADP. The reaction is linear to 400 mumol of ammonia per liter. The plasma sample volume is 100 microliter and the whole procedure takes only 25 min, including the 15-min preincubation. The normal range for venous plasma was 44 +/- 13.5 (SD) mumol of ammonia per liter.
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PMID:Two-point determination of plasma ammonia with the centrifugal analyzer. 20 86

The sequential pattern of lipid accumulation and associated biochemical changes were studied in two commonly used experimental models of nutritional fatty liver in rats. Female rats were maintained for 8 weeks on high fat, low protein diets containing adequate methionine and choline, and drinking water ad libitum (Diet 1), or deficient in methionine and choline and containing 20% ethanol as a substitute for drinking water (Diet 2). Histologically, there was a progressive increase in liver lipids, mainly in the periportal areas. Occasional foci of liver cell necrosis with lipogranuloma formation occurred in areas of severe fatty change. These changes appeared earlier and were more marked in rats maintained on Diet 2. Electron micrographs revealed large lipid droplets in the liver cells, which sometimes contained myelin figures. The mitochondria were enlarged, distorted and appeared as amorphous structures with disorientated cristae in rats on Diet 1, whereas they had a condensed conformation in rats maintained on Diet 2. Rough endoplasmic reticulum was fragmented and degranulated particularly in rats on Diet 1, and smooth endoplasmic reticulum showed hyperplasia and vesiculation in rats on Diet 2. There was a progressive increase in the total liver lipids and triglycerides in both the groups of rats. This fatty change was accompanied by a significant increase in hepatic 3-hydroxybutyrate, acetoacetate, malate, 2-oxoglutarate, citrate, lactate, ammonia, glutamate, alanine and aspartate, and a significant decrease in oxaloacetate, urea and glucose concentrations. The mass action ratios for alanine aminotransferase, aspartate amino transferase, and glutamate dehydrogenase, generally moved in a parallel direction. Hepatic ATP content was considerably reduced accompanied by a decrease in [ATP]/[ADP] ratios and a significant increased in [lactate]/[pyruvate] and [3-hydroxybutyrate]/[acetoacetate] ratios. There was a corresponding decrease in the [NAD+]/[NADH] ratios both in the cytoplasmic and mitochondrial compartments. These biochemical changes were particularly severe in rats maintained on Diet 1 and Diet 2 for 8 weeks. There was a very good relationship between impaired mitochondrial and endoplasmic reticulum functions, redox and phosphorylation states, and the relevance of their changes to the fate of fatty liver cells.
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PMID:Lipid accumulation in the rat liver: a histological and biochemical study. 23

Using the semi-continuous cultivation technique we could establish that specifically in Streptomyces noursei JA 3890b during growth on a medium supplied with D,L-alanine, NH4+, and maize starch there are two different phenotypes of the organism and stationary states of metabolism, respectively. The expression of either the metabolic state I with an enhanced capacity to oxidative deamination of alanine via the NAD+-dependent alanaine dehydrogenase or the metabolic state 2 which may be characterized by the preferred use of ammonium ions via the NADP+-dependent glutamate dehydrogenase was shown to depend strongly on the conditions of inoculum cultivation. When the amino acid permeases were derepressed by cultivating the inoculum cells on amino acid media, probably due to the defective mechanism of negative feedback control of amino acid influx in this strain an abnormously high uptake of alanine was observed that, consequently, was correlated to the enhanced oxidation of this amino acid as well as to the intensive production of ammonia within the cell. This overproduction of cellular NH4+ seems to bring about the subsequent repression of biosynthetic glutamate dehydrogenase and so on the accumulation of ammonia autocatalytically may rise up (metabolic state I). On the other hand, if the influx of alanine was kept low and the NADH oxidation was less efficient, respectively, or when there was high cellular activity of glutamate dehydrogenase the level of ammonia never did exceed the respressory limit and, accordingly, the expression of the metabolic state 2 was observed. Switching-over of metabolic flux from the state 2 towards the state 1 can be brought about either by increasing the level of nitrogen sources in the medium or by adding buffers pH greater than 7.5. In contrast, decrease of cellular level of NH4+ was shown to induce the transition of metabolic state 1 into the state 2. This can be achieved not only by limitation of nitrogen source but also by adding different aminobenzoic acids and, alternatively, effectors of membrane function (short-chain alcohols), inhibitors of cytochrome oxidases (sodium azide, potassium cyanide), heavy metal (Fe++)-chelating agents (catechol, 2,5'-dipyridyl, o-phenanthroline), beta-alanine, and buffers pH less than 7. This suggests that these effectors are capable of preventing the abnormously high influx of amino acids as well as its wasteful catabolism within the cell of S. noursei JA 3890b. Therefore, it seems likely that by this way the aminobenzoic acids and similar effectors can diminish the catabolite repression or inhibition of secondary metabolism by cellular excess of some nitrogen compounds in good agreement with its well-known stimulatory action on the biosynthesis of the antibiotic nourseothricin in this strain.
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PMID:Regulative influence of o-aminobenzoic acid on the biosynthesis of nourseothricin in cultures of Streptomyces noursei JA 3890b. IV. Bistability of metabolism and the mechanism of action of aminobenzoic acids. 23 65

The enzymes involved in the assimilation of ammonia by free-living cultures of Rhizobium spp. are glutamine synthetase (EC. 6.o.I.2), glutamate synthase (L-glutamine:2-oxoglutarate amino transferase) and glutamate dehydrogenase (ED I.4.I.4). Under conditions of ammonia or nitrate limitation in a chemostat the assimilation of ammonia by cultures of R. leguminosarum, R. trifolii and R. japonicum proceeded via glutamine synthetase and glutamate synthase. Under glucose limitation and with an excess of inorganic nitrogen, ammonia was assimilated via glutamate dehydrogenase, neither glutamine synthetase nor glutamate synthase activities being detected in extracts. The coenzyme specificity of glutamate synthase varied according to species, being linked to NADP for the fast-growing R. leguminosarum, R. melitoti, R. phaseoli and R. trifolii but to NAD for the slow-growing R. japonicum and R. lupini. Glutamine synthetase, glutamate synthase and glutamate dehydrogenase activities were assayed in sonicated bacteroid preparations and in the nodule supernatants of Glycine max, Vicia faba, Pisum sativum, Lupinus luteus, Medicago sativa, Phaseolus coccineus and P. vulgaris nodules. All bacteroid preparations, except those from M. sativa and P. coccineus, contained glutamate synthase but substantial activities were found only in Glycine max and Lupinus luteus. The glutamine synthetase activities of bacteroids were low, although high activities were found in all the nodule supernatants. Glutamate dehydrogenase activity was present in all bacteroid samples examined. There was no evidence for the operation of the glutamine synthetase/glutamate synthase system in ammonia assimilation in root nodules, suggesting that ammonia produced by nitrogen fixation in the bacteroid is assimilated by enzymes of the plant system.
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PMID:Ammonia assimilation by rhizobium cultures and bacteroids. 23 5

Methods are described in which liberation of ammonia from amino acid substrates by the D- and L-amino acid oxidases may be coupled with the NADH-dependent reductive amination of 2-oxoglutarate catalysed by exogenous glutamate dehydrogenase (L-glutamate: NAD oxidoreductase (deaminating), EC 1.4.1.2). The inhibition of D-amino acid oxidase (D-amino acid:O2 oxidoreductase (deaminating), EC 1.4.3.3) by ADP needed to activate and stabilise glutamate dehydrogenase was relieved by FAD, and the substrate was D-alanine at approximately 6-fold Km concentration. Neither FAD or FMN were required in the L-amino acid oxidase (L-amino acid:O2 oxidoreductase (deaminating), EC 1.4.3.2) assay; this utilised L-leucine as substrate in a concentration approximately 7-fold the Km value. The methods were reasonably sensitive and precise, and a linear relationship between activity and enzyme concentration prevailed up to an absorbance change of 0.050 per min. They have the advantage of being amenable to automation and to employment of fluorescence techniques should greater sensitivity be required.
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PMID:Coupled optical rate determinations of amino acid oxidase activity. 23 96

When Escherichia coli was grown in a minimum medium with glucose as sole carbon source and a proper level of ammonia, NADP+ specific glutamate dehydrogenase (L-glutamate: NADP+ oxidoreductase (deaminating), ED 1.4.1.4) was induced. The enzyme was solubilized by French press treatment and purified to homogeneity by (NH4)2SO4 fractionation, heat treatment followed by DEAE-cellulose, hydroxylapatite and Bio-Gel chromatography with an overall yield of 30%. The enzyme proved to be heat stable and relatively resistant to protein denaturants. The optimum of enzymic activity for the reductive amination is at pH 8 and at pH 9 for the oxidative deamination. The activity is affected by adenine nucleotides. The molecular weight (about 250 000 for the native form and 46 000 for the inactive subunit) and amino acid composition, suggest strict similarities with the NADP+ enzyme from fungal origin.
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PMID:Glutamate dehydrogenase from Escherichia coli: induction, purification and properties of the enzyme. 23 98

The activities of the following enzymes were studied in connection with dinitrogen fixation in pea bacteroids: glutamine synthetase(L-glutamate: ammonia ligase (ADP-forming)(EC 6.3.1.2)(GS); glutamate dehydrogenase (NADP+)(L-glutamate: NADP+ oxidoreductase (deaminating)(EC 1.4.1.4)(GDH); glutamate synthase (L-glutamine: 2-exeglutarate aminotransferase (NADPH-oxidizing))(EC 2.6.1.53)(GOGAT). GS activity was high throughout the growth of the plant and GOGAT activity was always low. It is unlikely that GDH or the GS-GOGAT pathway can account for the incorporation of ammonia from dinitrogen fixation in the pea bacteroid,
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PMID:Enzymes of ammonia assimilation in Rhizobium leguminosarum bacteroids. 23 31

A 250- to 300-fold purification of a nicotinamide adenine denucleotide phosphate (NADP)-dependent glutamate dehydrogenase (GDH, E.C. 1.4.1.4) with a yield of 60% from a thermophilic bacillus is described. More than one NADP-specific GDH was detected by polyacrylamide gel electrophoresis. The enzyme is of high molecular weight (approximately 2 X 10-6), similar to that of the beef and frog liver GDH. The pI of the thermophilic GDH is at pH 5.24. The enzyme is highly thermostable at the pH range of 5.8 to 9.0. The purified GDH, unlike the crude enzyme, was very labile at subzero temperatures. An unidentified factor(s) from the crude cell-free extract prevented the inactivation of the purified GDH at -70 C. Various reactants of the GDH system and D-glutamate also protected, to some extent, the enzyme from inactivation at -70 C. From the Michaelis constants for glutamate (1.1 X 10-2M), NADP (3 X 10-4M), ammonia (2.1 X 10-2M), alpha-ketoglutarate (1.3 X 10-3M), and reduced NADP (5.3 X 10-5M), it is suggested that the enzyme catalyzes in vivo the formation of glutamate from ammonia and alpha-ketoglutarate. The amination of alpha-ketoglutarate and deamination of glutamate by the thermophilic GDH are optimal at the pH values of 7.2 and 8.4, respectively.
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PMID:Purification and properties of glutamate dehydrogenase from a thermophilic bacillus. 23 42

Ammonia-nitrogen-limited continuous cultures of Escherichia coli and Klebsiella aerogenes contain induced levels of glutamine synthetase that is deadenylyated (i.e., fully active). In the presence of excess ammonia or glutamate in glucose-limited cultures of E. coli, glutamine synthetase is repressed and adenylylated (inactive). The average state of adenylylation (n) is a linear function of the specific growth rate. At low specific growth rates, glutamine synthetase is adenylylated; as the specific growth rate increases, n decreases, approaching 0 to 2 at rapid growth rates. The average state of adenylylation correlates well with the intracellular concentrations and ratios of alpha-ketoglutarate and glutamine, which are key effectors in the adenylylation-deadenylylation systems. E. coli and K. aerogenes differ markedly in their growth yields, growth rates, and enzymatic composition during nitrogen limitation. The data suggest that, unlike K. aerogenes, E. coli W uses glutamate dehydrogenase to incorporate ammonia during nitrogen limitation. In E. coli, glutamate dehydrogenase is progressively induced during nitrogen limitation when mu (growth rate) approaches mumax. In contrast, in K. aerogenes glutamate dehydrogenase is repressed during nitrogen limitation, whereas glutamate synthase, an alternative supplier of glutamate to the cell, is induced. Data are presented that support the regulatory schemes proposed for the control of glutamine synthetase activity by induction-repression phenomena and adenylylation-deadenylylation reaction. We propose that the intracellular ratio of alpha-ketoglutarate to glutamine may be the most important physiological parameter in determining the activity of glutamine synthetase.
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PMID:Regulation of nitrogen metabolism in Escherichia coli and Klebsiella aerogenes: studies with the continuous-culture technique. 23 54


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