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)

When grown autotrophically in a thiosulfate-mineral salts medium, cells of the facultative chemoautotrophic bacterium, Thiobacillus novellus, produced two distinct glutamate dehydrogenases, one specific for nicotinamide adenine dinucleotide phosphate (NADP) and the other specific for nicotinamide adenine dinucleotide (NAD). When glutamate was supplied exogenously as the sole carbon source, the NAD-specific glutamate dehydrogenase was fully induced. Lower levels of the enzyme were found in bacteria grown in l-arginine, l-alanine, glucose, glycerol, lactate, citrate, or succinate. Arginine, histidine, and aspartate, on the other hand, caused a marked repression of the NADP-specific glutamate dehydrogenase activity. The NAD-dependent glutamate dehydrogenase was allosteric. Adenosine-5'-monophosphate and adenosine-5'-diphosphate acted as positive effectors. Both glutamate dehydrogenases were purified about 250-fold and were shown to be distinct protein with different physical properties.
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PMID:Evidence for two species of glutamate dehydrogenases in Thiobacillus novellus. 438 66

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.
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PMID:The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm. 439 82

Acute renal failure induced by glycerol results in increased metabolism of glutamine by renal cortical slices of rats 16 and 36 hr after onset, and there is also increased glutamine uptake by the kidney in vivo. Metabolism of glutamine and glutamate to glucose is inhibited. At 8 days after onset of renal failure, metabolism of glutamine returns to normal. Initially, activities of phosphate-dependent glutaminase (PDG) and glutamate dehydrogenase are depressed. The activity of glutaminase returns to normal by 8 days, but glutamate dehydrogenase activity is still inhibited. Increased ammoniagenesis and glutamine uptake are mainly a result of increased entry into the cell since activity of glutaminase is inhibited.
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PMID:Renal metabolism of glutamine in rats with acute renal failure. 613 Nov 57

In mouse pancreatic islets the kinetics of insulin secretion and O2 uptake in response to the non-metabolizable leucine analogue (+/-)-BCH (2-endo- aminonorbornane -2-carboxylic acid) were compared. In addition, the fuel-mobilizing effect of (+/-)-BCH was studied with a mitochondrial fraction from islets. (1) Within 2 min 20 mM-(+/-)-BCH markedly enhanced insulin release or O2 consumption by islets respiring in the absence of exogenous fuels. During prolonged exposure to 20 mM-(+/-)-BCH secretion declined more rapidly than O2 uptake. (2) L-Glutamine (10 mM) prevented the decrease of both insulin release and O2 uptake of islets exposed to 20mM-(+/-)-BCH. During the second phase of insulin release in response to 20 mM-(+/-)-BCH + 10 mM-L-glutamine, kinetics of secretion and respiration correlated closely. (3) Initial peaks were consistently seen in the (+/-)-BCH-induced secretory profiles, but never in the respiratory profiles. (4) In contrast with L-glycerol 3-phosphate, L-malate or pyruvate, L-glutamine or L-glutamate maintained low rates of oxidative phosphorylation in B-cell mitochondria. The effects of L-glutamine or L-glutamate were potentiated severalfold by (+/-)-BCH. (5) The effects of other branched-chain amino acids on oxidative phosphorylation resembled their effects on insulin release, redox state of nicotinamide nucleotides and glutamate dehydrogenase activity. (6) The results support the view that (+/-)-BCH stimulates insulin secretion via a primary enhancement of hydrogen supply to the respiratory chain of B-cell mitochondria.
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PMID:Regulation of insulin secretion by energy metabolism in pancreatic B-cell mitochondria. Studies with a non-metabolizable leucine analogue. 637 87

Mitochondria isolated from systemic hearts of the squid Illex illecebrosus showed high respiratory control ratios, and, with appropriate substrates, the expected ADP/O ratios. Of amino acids tested, proline and ornithine were oxidized at highest rates; of carboxylates, malate, succinate and pyruvate gave the highest state-3 respiration rates. Pyruvate oxidation is enhanced with proline, ornithine, and 1-pyrroline-5-carboxylate (pyrroline carboxylate) all of which can serve to augment the Krebs cycle. However, proline, ornithine and pyrroline carboxylate oxidation is not similarly dependent upon pyruvate. Rotenone inhibited state-3 respiration of malate, proline, ornithine and pyrroline carboxylate. Neither intermediates of fatty acid oxidation nor glycerol 3-phosphate were utilized at significant rates. Key enzymes in proline and ornithine oxidation, i.e. proline dehydrogenase, pyrroline-carboxylate dehydrogenase, ornithine aminotransferase, and glutamate dehydrogenase were located in the mitochondria. The synthesis of proline is catalyzed by pyrroline-carboxylate reductase, which was found exclusively in the cytosol. The respiration, phosphorylation and enzyme data taken together suggest that the main carbon sources for heart mitochondria of Illex are pyruvate plus the proline and ornithine pool.
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PMID:Respiratory and enzymatic properties of squid heart mitochondria. 731 31

In renal tubules isolated from fed rabbits, 1 mM aspartate is mainly utilized for production of glutamine, glutamate, alanine, and serine, while it is not used for glucose synthesis. However, the addition of either 2 mM glycerol or 2 mM lactate, which are poor gluconeogenic substrates in renal tubules, results in acceleration of both glucose formation and incorporation of [14C]aspartate into glucose by several fold, accompanied by about a twofold decrease in glutamine synthesis and marked accumulation of glutamate and alanine. Ammonium release in renal tubules incubated with aspartate in the presence of methionine sulfoximine, an inhibitor of glutamine synthetase, is also decreased on the addition of glycerol and lactate by about two- and threefold, respectively. Since intracellular [glyceraldehyde 3-phosphate]/[3-phosphoglycerate], [glycerol 3-phosphate]/[dihydroxyacetone phosphate], [lactate]/[pyruvate], and intramitochondrial [glutamate]/[2-oxoglutarate] x [NH4+] ratios are increased in comparison with control values determined with aspartate alone, it is likely that the stimulatory effect of lactate and glycerol on glucose formation from aspartate may be due to (i) an increased availability of reducing equivalents in the cytosol resulting in an enhancement of glyceraldehyde-3-phosphate dehydrogenase activity and (ii) elevation of the mitochondrial NADH/NAD- ratio causing a decrease in glutamate dehydrogenase activity resulting in a diminished glutamine synthesis and enhanced provision of carbon skeleton of aspartate for gluconeogenesis. Stimulation of glucose formation in the presence of 1 mM aspartate + glycerol is not related to cell volume changes. However, an increase for about 30% of intracellular water space induced by 10 mM aspartate + glycerol is accompanied by both diminished gluconeogenesis and enhanced glutamine synthesis, compared with values measured with 1 mM aspartate plus glycerol.
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PMID:Glycerol and lactate induce reciprocal changes in glucose formation and glutamine production in isolated rabbit kidney-cortex tubules incubated with aspartate. 764 77

Islets were isolated by automatic digestion from non-diabetic cadaveric organ donors and from Type 2 (non-insulin-dependent) diabetic subjects. The activity of FAD-glycerophosphate dehydrogenase, but not that of either glutamate dehydrogenase, glutamate-oxalacetate transaminase or glutamate-pyruvate transaminase, was lower in Type 2 diabetic patients than control subjects. Hexokinase, glucokinase and glutamate decarboxylase activities were also measured in islets from control subjects. The utilization of D-[5-3H]glucose, oxidation of D-[6-14C]glucose and release of insulin evoked by D-glucose were all lower in Type 2 diabetic patients than control subjects. The secretory response to the combination of L-leucine and L-glutamine appeared less severely affected. Islets from Type 2 diabetic patients may thus display enzymatic, metabolic and secretory anomalies similar to those often observed in animal models of Type 2 diabetes, including a deficiency of beta-cell FAD-linked glycerophosphate dehydrogenase, the key enzyme of the glycerol phosphate shuttle.
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PMID:Enzymatic, metabolic and secretory patterns in human islets of type 2 (non-insulin-dependent) diabetic patients. 816 52

In islets from adult rats injected with streptozotocin during the neonatal period, both a nonmetabolized analog of L-leucine and 3-phenylpyruvate augmented 14CO2 output from islets either prelabeled with L-[U-14C]glutamine or exposed to D-[2-14C]glucose and D-[6-14C]glucose, in a manner qualitatively comparable to that found in islets from control rats. The islets of diabetic rats differed, however, from those of control rats by their unresponsiveness to both the L-leucine analog and a high concentration of D-glucose in terms of increasing 3HOH generation from [2-3H]glycerol, an impaired sparing action of the hexose upon 14CO2 output from islets prelabeled with [U-14C]palmitate, and, most importantly, by a decreased rate of D-[2-14C]glucose and D-[6-14C]glucose oxidation when either incubated at a high concentration of the hexose (16.7 mM) or stimulated by nonglucidic nutrient secretagogues at a low concentration of D-glucose (2.8 mM). In islet homogenates, the activity of glyceraldehyde phosphate dehydrogenase, glutamate decarboxylase, and NADP-malate dehydrogenase was lower in diabetic than control islets. Such was not the case for glutamate-alanine transaminase, glutamate-aspartate transaminase, or glutamate dehydrogenase. The neonatal injection of streptozotocin thus affected, in the adult rats, the activity of several islet enzymes. Nevertheless, the metabolic data suggest that an impaired circulation in the glycerol phosphate shuttle, as observed in response to stimulation of the islets by either a high concentration of D-glucose or nonglucidic nutrient secretagogues, represents an essential determinant of the preferential impairment of glucose-induced insulin release in this model of non-insulin-dependent diabetes.
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PMID:Metabolic response to nonglucidic nutrient secretagogues and enzymatic activities in pancreatic islets of adult rats after neonatal streptozotocin administration. 848 60

In Saccharomyces cerevisiae, carbon and nitrogen metabolisms are connected via the incorporation of ammonia into glutamate; this reaction is catalyzed by the NADP-dependent glutamate dehydrogenase (NADP-GDH) encoded by the GDH1 gene. In this report, we show that the GDH1 gene requires the CCAAT box-binding activator (HAP complex) for optimal expression. This conclusion is based on several lines of evidence: (1) overexpression of GDH1 can correct the growth defect of hap2 and hap3 mutants on ammonium sulfate as a nitrogen source, (ii) Northern (RNA) blot analysis shows that the steady-state level of GDH1 mRNA is strongly lowered in a hap2 mutant, (iii) expression of a GDH1-lacZ fusion is drastically reduced in hap mutants, (iv) NADP-GDH activity is several times lower in the hap mutants compared with that in the isogenic wild-type strain, and finally, (v) site-directed mutagenesis of two consensual HAP binding sites in the GDH1 promoter strongly reduces expression of GDH1 and makes it HAP independent. Expression of GDH1 is also regulated by the carbon source, i.e., expression is higher on lactate than on ethanol, glycerol, or galactose, with the lowest expression being found on glucose. Finally, we show that a hap2 mutation does not affect expression of other genes involved in nitrogen metabolism (GDH2, GLN1, and GLN3 encoding, respectively, the NAD-GDH, glutamine synthetase, and a general activator of several nitrogen catabolic genes). The HAP complex is known to regulate expression of several genes involved in carbon metabolism; its role in the control of GDH1 gene expression, therefore, provides evidence for a cross-pathway regulation between carbon and nitrogen metabolisms.
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PMID:The CCAAT box-binding factor stimulates ammonium assimilation in Saccharomyces cerevisiae, defining a new cross-pathway regulation between nitrogen and carbon metabolisms. 860 56

An NADP(H)-specific glutamate dehydrogenase of Haloferax mediterranei has been purified to apparent homogeneity and characterised. The purified enzyme was stabilized by glycerol in absence of salt. Glutamate dehydrogenase from Hf. mediterranei is a hexameric enzyme with a native molecular mass of 320 kDa composed of monomers each with a molecular mass of 55 kDa. At pH 8.5 the enzyme has Kms of 0.018, 0.34 and 4.2 mM for NADP+, 2-oxoglutarate and ammonium, respectively. Amino acid composition and sequence of the first 16 residues of the N-terminus have been determined.
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PMID:NADP-glutamate dehydrogenase from the halophilic archaeon Haloferax mediterranei: enzyme purification, N-terminal sequence and stability. 906 51


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