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)

Glutamate dehydrogenase (GDH, EC 1.4.1.2) catalyzes the synthesis and degradation of glutamate, an excitatory neurotransmitter in the retina. Recently, two forms of GDH, a soluble heat-stable form and a particulate heat-labile form, have been demonstrated to be deficient in some types of spinocerebellar degeneration (SCD). We measured these forms of GDH activity in leukocyte homogenate from patients with SCD (n = 22) and normal subjects (n = 20) who were examined ophthalmoscopically and electrophysiologically. Seven patients with SCD showed attenuated oscillatory potentials (OPs) on electroretinography. The heat-labile GDH activity in these seven patients (78 +/- 51 nmol/mg protein/h) was significantly lower than that of 15 patients with normal OPs (367 +/- 189) and the normal subjects (397 +/- 1720 (P less than 0.001). Our results indicated that patients with SCD could be separated into two groups electrophysiologically, one with normal OPs and one with attenuated OPs. Also indicated was that a deficiency of heat-labile GDH might affect some functions of neural elements in the retina that are responsible for the generation of OPs.
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PMID:Partially deficient glutamate dehydrogenase activity and attenuated oscillatory potentials in patients with spinocerebellar degeneration. 174 Mar 78

Glutamate dehydrogenase (L-glutamate:NAD(P)+ oxidoreductase, deaminating, EC 1.4.1.3.) of the extreme thermophilic archaebacterium Sulfolobus solfataricus was purified to homogeneity by (NH4)2SO4 fractionation, anion-exchange chromatography and affinity chromatography on 5'-AMP-Sepharose. The purified native enzyme had a Mr of about 270,000 and was shown to be a hexamer of subunit Mr of 44,000. It was active from 30 to 95 degrees C, with a maximum activity at 85 degrees C. No significant loss of enzyme activity could be detected, either after incubation of the purified enzyme at 90 degrees C for 60 min, or in the presence of 4 M urea or 0.1% SDS. The enzyme was catalytically active with both NADH and NADPH as coenzyme and was specific for 2-oxoglutarate and L-glutamate as substrates. With respect to coenzyme utilization the Sulfolobus solfataricus glutamate dehydrogenase resembled more closely the equivalent enzymes from eukaryotic organisms than those from eubacteria.
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PMID:Purification and properties of an extreme thermostable glutamate dehydrogenase from the archaebacterium Sulfolobus solfataricus. 189 41

Frankia spp. are filamentous actinomycetes that fix N2 in culture and in actinorhizal root nodules. In combined nitrogen-depleted aerobic environments, nitrogenase is restricted to thick-walled spherical structures, Frankia vesicles, that are formed on short stalks along the vegetative hyphae. The activities of the NH4(+)-assimilating enzymes (glutamine synthetase [GS], glutamate synthase, glutamate dehydrogenase, and alanine dehydrogenase) were determined in cells grown on NH4+ and N2 and in vesicles and hyphae from N2-fixing cultures separated on sucrose gradients. The two frankial GSs, GSI and GSII, were present in vesicles at levels similar to those detected in vegetative hyphae from N2-fixing cultures as shown by enzyme assay and two-dimensional polyacrylamide gel electrophoresis. Glutamate synthase, glutamate dehydrogenase, and alanine dehydrogenase activities were restricted to the vegetative hyphae. Vesicles apparently lack a complete pathway for assimilating ammonia beyond the glutamine stage.
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PMID:Enzymes of ammonia assimilation in hyphae and vesicles of Frankia sp. strain CpI1. 196 54

Sensitive flow-injection analyses of aspartate, glutamate, 2-oxoglutarate, and oxaloacetate were developed. The analytes were enzymatically coupled with NADH which was monitored by light emission from immobilized bacterial bioluminescence enzymes. Aspartate (or oxaloacetate) was assayed on the basis of NADH consumption by introducing the sample through a coimmobilized aspartate aminotransferase-malate dehydrogenase column. The assay responded linearly from 100 pmoles to 5 nmoles per assay. Glutamate (2-oxoglutarate) was determined by formation of NADH in the glutamate dehydrogenase reaction. The measuring range for glutamate was from 10 pmoles to 100 nmoles per assay. The precision of the flow-injection method was generally excellent, and the sensitivities of the described assays were 100-1000-fold higher than with spectrophotometric methods. The immobilized enzyme preparations were stable for several months in storage, and the enzyme columns could be used for 600-800 analyses. Flow-injection analyses of amino acids and related compounds by NADH/bioluminescence-coupled reactions provide a sensitive, fast, and inexpensive assay method for a wide variety of purposes.
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PMID:Flow-injection analysis of amino acids and their metabolites by immobilized vitamin B6-dependent enzymes. Sensitive determination of L-aspartate, L-glutamate, 2-oxoglutarate, and oxaloacetate. 197 15

We utilized gas chromatography-mass spectrometry to study the transfer of 15N from [2-15N]glutamine, [15N]leucine, [15N]alanine, or 15NH4Cl to [15N]glutamate and [15N]aspartate in cultured cerebrocortical GABA-ergic neurons from the mouse. Initial rates of 15N appearance (atom % excess) were somewhat higher with 2mM [2-15N]glutamine as a precursor than with 1mM [15N]leucine or 1mM [15N]alanine, but initial net formation (nmol [15N]glutamate/mg protein.min-1) was roughly comparable with all precursors. At steady-state 15N labeling was about two times greater with 2mM [2-15N]glutamine as precursor. The subsequent transfer of 15N from glutamate to aspartate was extremely rapid, the labelling pattern of these two amino acid pools being virtually indistinguishable. We observed little reductive amination of 2-oxo-glutarate to yield [15N]glutamate in the presence of 0.3mM 15NH4Cl. Reductive amination through glutamate dehydrogenase was much more prominent at a concentration of 3.0mM 15NH4Cl. Glutamate formation via reductive amination was unaffected by inclusion of 1mM 2-oxo-glutarate in the incubation medium. These results indicate that glutamate synthesis in cultured GABA-ergic neurons is derived not only from the glutaminase reaction, but also from transamination reactions in which both leucine and alanine are efficient N donors. Reductive amination of 2-oxo-glutarate in the glutamate dehydrogenase pathway plays a relatively minor role at lower concentrations of extracellular ammonia but becomes quite active at 3mM ammonia.
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PMID:Precursors of glutamic acid nitrogen in primary neuronal cultures: studies with 15N. 209 13

Evidence for the existence of a glutamine cycle in Neurospora crassa is reviewed. Through this cycle glutamine is converted into glutamate by glutamate synthase and catabolized by the glutamine transaminase-omega-amidase pathway, the products of which (2-oxoglutarate and ammonium) are the substrates for glutamate dehydrogenase-NADPH, which synthesizes glutamate. In the final step ammonium is assimilated into glutamine by the action of a glutamine synthetase (GS), which is formed by two distinct polypeptides, one catalytically very active (GS beta), and the other (GS alpha) less active but endowed with the capacity to modulate the activity of GS alpha. Glutamate synthase uses the amide nitrogen of glutamine to synthesize glutamate; glutamate dehydrogenase uses ammonium, and both are required to maintain the level of glutamate. The energy expended in the synthesis of glutamine drives the cycle. The glutamine cycle is not futile, because it is necessary to drive an effective carbon flow to support growth; in addition, it facilitates the allocation of nitrogen or carbon according to cellular demands. The glutamine cycle which dissipates energy links catabolism and anabolism and, in doing so, buffers variations in the nutrient supply and drives energy generation and carbon flow for optimal cell function.
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PMID:Glutamine metabolism and cycling in Neurospora crassa. 214 4

1. Glutamine was found to be the main carbon and nitrogen product of the metabolism of aspartate in isolated guinea-pig kidney-cortex tubules. Glutamate, ammonia and alanine were only minor products. 2. Carbon-balance calculations and the release of 14CO2 from [U-14C]aspartate indicate that oxidation of the aspartate carbon skeleton occurred. 3. A pathway involving aspartate aminotransferase, glutamate dehydrogenase, glutamine synthetase, phosphoenolpyruvate carboxykinase, pyruvate kinase, pyruvate dehydrogenase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of aspartate into glutamine. 4. Evidence for this pathway was obtained by: (i) inhibiting aspartate removal by amino-oxyacetate, an inhibitor of transaminases, (ii) the use of methionine sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from aspartate, (iii) the use of quinolinate, an inhibitor of phosphoenolpyruvate carboxykinase, which inhibited glutamine synthesis from aspartate, (iv) the use of alpha-cyano-4-hydroxycinnamate, an inhibitor of the mitochondrial transport of pyruvate, which caused an accumulation of pyruvate from aspartate, and (v) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from aspartate.
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PMID:Glutamine synthesis from aspartate in guinea-pig renal cortex. 236 82

The activity of glutamate related enzymes and the concentration of glutamine, glutamate and gamma-amino n-butyric acid (GABA) were investigated in the cerebral cortex of rats, in different stages of insulin-induced hypoglycemia. Hypoglycemia was produced by intraperitoneal injection of insulin 0.05-100 units per kg body weight. The minimum required dose to produce irreversible severe hypoglycemia was 0.5 units/kg. In 85% of the cases an insulin induced hypoglycemic convulsion, was achieved 130-150 minutes after injection. Blood glucose levels during insulin induced seizures ranged between 8-15 mg%. In the range of 0.5-100 u insulin/kg the degree of hypoglycemia and the onset of convulsions were identical. The concentration of glutamine was significantly reduced during convulsive and postconvulsive stages. Glutamate and GABA concentrations were reduced significantly in all stages of insulin-induced hypoglycemia. The decrease in glutamine concentration was concurrent with an increase in the activity of its degradative enzyme, glutaminase. This was apparent at the preconvulsive, convulsive and postconvulsive stages. The activity of other enzymes related to energy production such as glutamate dehydrogenase (GDH), glutamate transaminase (GPT) and aspartate aminotransferase (AAT) were also increased. The activity of glutamine synthase (GS) was unaffected by hypoglycemia. Insulin induced changes in glutamine, glutamate and their related enzymes could not be attributed to convulsion since a similar pattern of changes was observed in the preconvulsive and postconvulsive stages, and no changes were detected following picrotoxin-induced seizures.
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PMID:Changes in the activity of glutamate related enzymes in cerebral cortex, during insulin-induced seizures. 257 18

NADP+-specific glutamate dehydrogenase from Salmonella typhimurium, cloned and expressed in Escherichia coli, has been purified to homogeneity. The nucleotide sequence of S. typhimurium gdhA was determined and the amino acid sequence derived. The nucleotide analogue 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate (2-BDB-T epsilon A-2',5'-DP) reacts irreversibly with the enzyme to yield a partially inactive enzyme. After about 60% loss of activity, no further inactivation is observed. The rate of inactivation exhibits a nonlinear dependence on 2-BDB-T epsilon A-2',5'-DP concentration with kmax = 0.160 min-1 and KI = 300 microM. Reaction of 200 microM 2-BDB-T epsilon A-2',5'-DP with glutamate dehydrogenase for 120 min results in the incorporation of 0.94 mol of reagent/mol of enzyme subunit. The coenzymes, NADPH and NADP+, completely protect the enzyme against inactivation by the reagent and decrease the reagent incorporation from 0.94 to 0.5 mol of reagent/mol enzyme subunit, while the substrate alpha-ketoglutarate offers only partial protection. These results indicate that 2-BDB-T epsilon A-2',5'-DP functions as an affinity label of the coenzyme binding site and that specific reaction occurs at only about 0.5 sites/enzyme subunit or 3 sites/hexamer. Glutamate dehydrogenase modified with 200 microM 2-BDB-T epsilon A-2',5'-DP in the absence and presence of coenzyme was reduced with NaB3H4, carboxymethylated, and digested with trypsin. Labeled peptides were purified by high performance liquid chromatography and characterized by gas phase sequencing. Two peptides modified by the reagent were isolated and identified as follows: Phe-Cys(CM)-Gln-Ala-Leu-Met-Thr-Glu-Leu-Tyr-Arg and Leu-Cys(CM)-Glu-Ile-Lys. These two peptides were located within the derived amino acid sequence as residues 146-156 and 282-286. In the presence of NADPH, which completely prevents inactivation, only peptide 146-156 was labeled. This result indicates that modification of the pentapeptide causes loss of activity. Glutamate 284 in this peptide is the probable reaction target and is located within the coenzyme binding site.
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PMID:Affinity labeling of a glutamyl peptide in the coenzyme binding site of NADP+-specific glutamate dehydrogenase of Salmonella typhimurium by 2-[(4-bromo-2,3-dioxobutyl)thio]-1,N6-ethenoadenosine 2',5'-bisphosphate. 265 14

The influence of ageing on glutamate dehydrogenase activity was studied in the cerebellar cortex of 3-month-old (young), 12-month-old (adult) and 26-month-old (aged) male Sprague-Dawley rats by using an enzyme histochemical technique. In young rats the enzyme reactivity was observed in the neuropil of the molecular layer as well as in the perikarya of basket cells and of stellate cells; within the cytoplasm of Purkinje neurons and in synaptic glomeruli of the granular layer. Glutamate dehydrogenase activity was significantly increased in the cerebellar cortex of adult rats and decreased in old animals. The synaptic glomeruli of the granular layer were the structures of the cerebellar cortex more remarkably affected by age-related changes. The possibility that decreased glutamate catabolism occurring in the ageing cerebellar cortex may result in an excess of the amino acid and may contribute to the nerve cell loss occurring in the cerebellum of old rats is discussed.
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PMID:Enzyme histochemistry of glutamate dehydrogenase in ageing rat cerebellar cortex. 271 67


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