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)

Glutamate synthase from Escherichia coli K-12 exhibits NH3-dependent activity. NH3-dependent activity is increased approximately 5-fold in apoglutamate synthase lacking flavin and non-heme iron. Whereas glutamine plus 2-oxoglutarate have the capacity to reoxidize the chemically reduced flavoenzyme, no such reoxidation is obtained with 2-oxoglutarate plus NH3. These results establish that the glutamine- and NH3-dependent syntheses of glutamate occur by different pathways of electron transfer from NADPH. The NH3-dependent activity of native and apoglutamate synthase exhibits similar catalytic properties. Some properties of apoglutamate synthase are similar to those of glutamate dehydrogenase. These properties include pH optima for synthesis and oxidative deamination of glutamate, inactivation by alkylating reagents and p-mercuribenzoate, an enhanced rate of inactivation by alkylating reagents and p-mercuribenzoate at low pH, 2-oxoglutarate protection against inactivation by p-mercuribenzoate, and reactivation of p-mercuribenzoate-treated enzyme by 2-mercaptoethanol. 2-Oxoglutarate protects against alkylation of glutamate synthase by iodo [1-14C]acetamide and reduces incorporation of methyl [1-14C]carboxamide into the small subunit of the enzyme.
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PMID:Properties of apoglutamate synthase and comparison with glutamate dehydrogenase. 0 50

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

Methscopolamine was used to induce ruminal stasis in calves. Clinical and blood biochemical parameters were studied to judge the possible role of gastro-intestinal endotoxins from Gram-negative bacteria. Two trials were carried out where one injection of 100 mg and 3 consecutive injections of 70 mg of methscopolamine were administered. The animals showed signs of ruminal stasis. General clinical signs and changes in blood biochemical parameters were similar to what is found in endotoxaemia or in induced ruminal acidosis. Relevant parameters such as prostaglandin F2 alpha metabolite, endotoxin, iron, zinc, calcium and glutamate dehydrogenase changed significantly indicating exposure of endotoxins.
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PMID:The role of endotoxins in methscopolamine induced ruminal stasis in calves. 150 96

Incubation of isolated rat hepatocytes with 0.1 mM iron nitrilotriacetic acid (FeNTA) caused a rapid rise in lipid peroxidation followed by a substantial increase in trypan blue staining and lactate dehydrogenase release, but did not affect the protein and non-protein thiol content of the cells. Hepatocyte death was preceded by the decline of mitochondrial membrane potential, as assayed by rhodamine 123 uptake, and by the depletion of cellular ATP. Chelation of extracellular Ca2+ by ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid or inhibition of Ca2+ cycling within the mitochondria by LaCl3 or cyclosporin A did not prevent the decline of rhodamine 123 uptake. On the other hand, a dramatic increase in the conjugated diene content was observed in mitochondria isolated from FeNTA-treated hepatocytes. Oxidative damage of mitochondria was accompanied by the leakage of matrix enzymes glutamic oxalacetic aminotransferase (GOT) and glutamate dehydrogenase (GLDH). The addition of the antioxidant N,N'-diphenylphenylene diamine (DPPD) completely prevented GOT and GLDH leakage, inhibition of rhodamine 123 uptake, and ATP depletion induced by FeNTA, indicating that Ca(2+)-independent alterations of mitochondrial membrane permeability consequent to lipid peroxidation were responsible for the loss of mitochondrial membrane potential. DPPD addition also protected against hepatocyte death. Similarly hepatocytes prepared from fed rats were found to be more resistant than those obtained from starved rats toward ATP depletion and cell death caused by FeNTA, in spite of undergoing a comparable mitochondrial injury. A similar protection was also observed following fructose supplementation of hepatocytes isolated from starved rats, indicating that the decline of ATP was critical for the development of FeNTA toxicity. From these results it was concluded that FeNTA-induced peroxidation of mitochondrial membranes impaired the electrochemical potential of these organelles and led to ATP depletion which was critical for the development of irreversible cell injury.
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PMID:Mitochondrial damage and its role in causing hepatocyte injury during stimulation of lipid peroxidation by iron nitriloacetate. 163 73

Changes in blood chemistry were examined in vitamin B12 deficient lambs which developed ovine white-liver disease (OWLD), and were compared with values of cobalt/B12 supplemented lambs on the same pastures, as well as clinically healthy, but sometimes B12 deficient, lambs on other pastures (H). In the OWLD group, signs of hepatic damage were seen concurrently with reduction in weight gain, or 1-3 weeks before, and comprised elevation of serum glutamate dehydrogenase (GLDH) and decrease of phospholipid and cholesterol. Drop of plasma glucose and elevation of gamma GT also came in the earlier phase of the disease. All other blood changes developed later, and were partly regarded as reflections of the inappetence or hepatic injury. The changes included a drop in packed cell volume (PCV) and mean corpuscular volume (MCV), elevation of serum iron, and reduction of total serum protein and urea. Generally Co/B12 supplementation prevented hepatic damage and normalized blood values. The clinically healthy H lambs also showed signs of hepatic damage, especially one year when they were B12 deficient, indicating that simple B12 deficiency causes a moderate liver damage as well. For diagnostic purposes, clinical pathology is recommended mainly on a flock basis.
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PMID:Ovine white-liver disease (OWLD). Changes in blood chemistry. 208 Jul 72

The hepatotoxic and lipid peroxidative potentials of t-butyl hydroperoxide (t-BuOOH) towards isolated perfused rat livers were investigated at doses of 1 and 3 mmol l-1. t-BuOOH led to a concentration-dependent release of cytosolic (glutamate-pyruvate transaminase and lactate dehydrogenase) and mitochondrial (glutamate dehydrogenase) enzymes, an accumulation of calcium in the liver, a marked depletion of hepatic glutathione and an enhanced release of it into the perfusate, as well as an enhanced formation and release of malondialdehyde (MDA) by the liver. These effects were blocked in the presence of the potent iron chelator deferrioxamine, and enhanced in livers from iron-overloaded as well as in livers from glutathione-depleted rats. Our results indicate that the hepatotoxic and pro-oxidant actions of organic hydroperoxides depend upon the presence of ionized iron as a catalyst of radical-forming breakdown reactions, and are potentiated by impairment of glutathione-dependent detoxification reactions.
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PMID:The role of iron and glutathione in t-butyl hydroperoxide-induced damage towards isolated perfused rat livers. 225 82

The glutamine synthetase and the NADP-specific glutamate dehydrogenase activities of Neurospora crassa were lost in a culture without carbon source only when in the presence of air. Glutamine synthetase was previously reported to be liable to in vitro and in vivo inactivation by activated oxygen species. Here we report that NADP-specific glutamate dehydrogenase was remarkably stable in the presence of activated oxygen species but was rendered susceptible to oxidative inactivation when chelated iron was bound to the enzyme and either ascorbate or H2O2 reacted on the bound iron. This reaction gave rise to further modifications of the enzyme monomers by activated oxygen species, to partial dissociation of the oligomeric structure, and to precipitation and fragmentation of the enzyme. The in vitro oxidation reaction was affected by pH, temperature, and binding to the enzyme of NADPH. Heterogeneity in total charge was observed in the purified and immunoprecipitated enzymes, and the relative amounts of enzyme monomers with different isoelectric points changes with time of the oxidizing reaction.
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PMID:Oxidation of Neurospora crassa NADP-specific glutamate dehydrogenase by activated oxygen species. 253 Feb 8

Early iron deficiency in rat does not affect the weight or the protein, DNA, and RNA content but results in a slight reduction in gamma-aminobutyric acid (GABA) (13%, p less than 0.01) and glutamic acid (20%, p less than 0.001) content of the brain. The activities of the two GABA shunt enzymes, glutamate dehydrogenase and GABA-transaminase, and of the NAD+-linked isocitrate dehydrogenase (ICDH) were inhibited whereas the glutamic acid decarboxylase, mitochondrial NADP+-linked ICDH, and succinic dehydrogenase activities remained unaltered in brain. On rehabilitation with the iron-supplemented diet for 1 week, these decreased enzyme activities in brain attained the corresponding control values. However, the hepatic nonheme iron content increased to about 80% of the control, after rehabilitation for 2 weeks. A prolonged iron deficiency resulting in decreased levels of glutamate and GABA may lead to endocrinological, neurological, and behavioral alterations.
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PMID:Effect of early iron deficiency in rat on the gamma-aminobutyric acid shunt in brain. 287 Nov 28

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

Using fully mechanized analytical equipment, interference by haemolysis in the determination of 26 clinical chemical parameters was determined quantitatively by adding haemolysate to serum. Haemoglobin concentrations up to 6.6 g/l caused essentially no interference in the following determinations: albumin (immuno-nephelometric), alpha-amylase, calcium, chloride, cholesterol, cholinesterase, creatinine, iron, glucose, glutamate dehydrogenase, uric acid, urea, sodium, inorganic phosphate, total protein, transferrin and triglycerides. In the presence of haemoglobin, erroneously high values were found for: lactate dehydrogenase (haemoglobin higher than 0.2 g/l), aspartate aminotransferase, potassium and acid phosphate (haemoglobin higher than 1.5 g/l), creatine kinase (haemoglobin higher than 2.5 g/l) and alanine aminotransferase (haemoglobin higher than 3.4 g/l). Erroneously low values were found for bilirubin (haemoglobin higher than 0.8 g/l), alkaline phosphatase and albumin (by electrophoresis) (haemoglobin higher than 1.5 g/l) and gamma-glutamyltransferase (haemoglobin higher than 3.0 g/l).
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PMID:Haemolysis as an interference factor in clinical chemistry. 371 97


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