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:1.4.3.11 (glutamate dehydrogenase)
4,437 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. On transferring Clostridium symbiosum glutamate dehydrogenase from pH 7 to assay mixtures at pH 8.8, reaction time courses showed a marked deceleration that was not attributable to the approach to equilibrium of the catalysed reaction. The rate became approximately constant after declining to 4-5% of the initial value. Enzyme, stored at pH 8.8 and assayed in the same mixture, gave an accelerating time course with the same final linear rate. The enzyme appears to be reversibly converted from a high-activity form at low pH to a low-activity form at high pH. 2. Re-activation at 31 degrees C upon dilution from pH 8.8 to pH 7 was followed by periodic assay of the diluted enzyme solution. At low ionic strength (5 mM-Tris/HCl), no re-activation occurred, but various salts promoted re-activation to a limiting rate, with full re-activation in 40 min. 3. Re-activation was very temperature-dependent and extremely slow at 4 degrees C, suggesting a large activation energy. 4. 2-Oxoglutarate, glutarate or succinate (10 mM) accelerated re-activation; L-glutamate and L-aspartate were much less effective. 5. The monocarboxylic amino acids alanine and norvaline appear to stabilize the inactive enzyme: 60 mM-alanine does not promote re-activation, and, as substrates at pH 8.8 for enzyme stored at pH 7, alanine and norvaline give progress curves showing rapid complete inactivation. 6. Mono- and di-nucleotides (AMP, ADP, ATP, NAD+, NADH, NADP+, CoA, acetyl-CoA) at low concentrations (10(-4)-10(-3) M) enhance re-activation at pH 7 and also retard inactivation at pH 8.8. 7. The re-activation rate is independent of enzyme concentration: ultracentrifuge experiments show no changes in molecular mass with or without substrates. 8. The activation-inactivation appears to be due to a slow pH-dependent conformational change that is sensitively responsive to the reactants and their analogues.
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PMID:A pH-dependent activation-inactivation equilibrium in glutamate dehydrogenase of Clostridium symbiosum. 224 20

A photoactive coenzyme analog of NAD+ has been synthesized by chemically coupling [32P]2-azido-AMP and NMN to produce [32P]nicotinamide 2-azidoadenosine dinucleotide (2-azido-NAD+). The utility of 2-azido-NAD+ as an effective active-site-directed photoprobe was demonstrated using bovine liver glutamate dehydrogenase as a model enzyme. In the absence of ultraviolet light, 2-azido-NAD+ is a substrate for this enzyme. Photoincorporation of probe was saturable with two different apparent dissociation constants of 10 microM and 40 microM. Protection of photoinsertion was seen with the natural substrate NAD+ with apparent dissociation constants of less than 5 microM and 25 microM. This observation may be explained on the basis of negative cooperative interaction between the subunits. The photoinsertion of 2-azido-NAD+ was increased by GTP and decreased by ADP in accordance with their known effects on NAD+ binding. When the enzyme was covalently modified by photolysis in the presence of saturating amounts of photoprobe, an approximately 40% inhibition of the enzyme activity was observed. These results demonstrate that the photoaffinity coenzyme analog has potential application as a probe to characterize NAD(+)-binding proteins and to identify the active sites of these proteins.
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PMID:Synthesis and properties of 2-azido-NAD+. A study of interaction with glutamate dehydrogenase. 230 69

The effect of nucleotides: AMP, cAMP, ADP, ATP, GDP and GTP, on glutamate dehydrogenase (GDH) purified from the mealworm fat body was studied. Guanine nucleotides and ATP inhibited the enzyme strongly in both directions. GDH was partially protected from the inhibition by the addition of ADP to an assay medium. AMP and cAMP activated the enzyme slightly. The concerted effects of ADP and ATP indicate the importance of adenylate energy charge in the regulation of fat body GDH. It is suggested that GDH may play amphibolic role in the fat body and that the direction of GDH catalysed reaction is under strong influence of nucleotides. The enzyme may synthesize glutamate at high energy charge, but when the energy reserves are low, it oxidizes glutamate.
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PMID:The effect of nucleotides on glutamate dehydrogenase from the mealworm fat body. 245 16

In monolayer cultures, hepatocyte-specific enzymes are inducible by hormones as soon as hepatocytes differentiate from the embryonic foregut (15-somite stage). Though offering an excellent opportunity for quantitative studies, several features of a normal cell environment are lost in such a model system. To determine the inducibility of such tissue-specific enzymes in intact organisms, rat embryos were cultured in vitro for 48 h and exposed to the hormonal factors that had been found effective in monolayer culture, viz. dexamethasone, triiodothyronine and dibutyryl cyclic AMP. Normal development of the embryos during culture in vitro was assessed by general criteria reflecting growth, morphogenesis and cytodifferentiation. Development of external features, organogenesis, the distribution of cell divisions and the appearance of tissue-specific proteins such as alpha-fetoprotein and glutamate dehydrogenase served as parameters. Despite undisturbed development of the embryos as judged by these criteria, irrespective of whether the culture was started at day 10 or at day 11 of gestation (just before, respectively after the appearance of the liver primordium), induction of hepatocyte-specific enzymes like carbamoylphosphate synthetase by hormones could not be demonstrated immunohistochemically. However, induction of this enzyme by hormones could be demonstrated in monolayers of hepatocytes isolated from such embryos after 48 h of culture, providing yet another demonstration of the adequate culture conditions. In addition, an adequate uptake of hormones by the embryo during culture could be shown with radio-actively labeled dexamethasone and triiodothyronine and with a radioreceptor assay for cyclic AMP. Therefore, the presence of factors in young embryos that inhibit tissue-specific enzyme synthesis has to be postulated.
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PMID:Hormonal inducibility of liver-specific enzymes in cultured rat embryos. 282 35

Enzymatic dephosphorylation of the phosphorylated forms of five different yeast enzymes has been studied: fructose-1,6-bisphosphatase, glycogen phosphorylase, neutral trehalase, NAD-glutamate dehydrogenase and 6-phosphofructo-2-kinase. Phosphorylated fructose-1,6-bisphosphatase and phosphorylated 6-phosphofructo-2-kinase were present in extracts of starved yeast cells which had been incubated for 10 min with glucose. Phosphorylated glycogen phosphorylase, neutral trehalase and NAD-glutamate dehydrogenase were obtained by incubation of yeast extract with ATP, cyclic AMP and Mg2+. After incubation with commercially available preparations of alkaline phosphatase, all five phosphorylated enzymes studied showed the changes in catalytic activity that would be expected as a consequence of dephosphorylation. The recently purified yeast enzyme which dephosphorylates phosphorylated fructose-1,6-bisophosphatase (Horn and Holzer (1987) however, was found to be active only with the phosphorylated fructose-1,6-bisphosphatase, but not with the other four phosphorylated enzymes studied. By contrast, a crude extract from yeast showed dephosphorylating activity towards all five substrates. Substrate specificity with the five phosphorylated enzymes studied of different phosphoprotein phosphatases from yeast prepared by others is discussed.
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PMID:Substrate specificity of the phosphorylated fructose-1,6-bisphosphatase dephosphorylating protein phosphatase from Saccharomyces cerevisiae. 284 61

The NAD-dependent glutamate dehydrogenase from Phycomyces spores was purified more than 300-fold. Estimation of Mr by gel filtration gave a value of 98,000 whereas after SDS-PAGE one major band of Mr 54,000 was found, suggesting that the enzyme is a dimer. The enzyme was virtually dependent on the presence of AMP for activity and showed half-maximal activation at 9.5 and 43 microM-AMP in the direction of animation and deamination respectively. ADP was nearly as effective at 20-fold higher concentrations. Other nucleotide monophosphates were ineffective and nucleoside triphosphates were slightly inhibitory. Hyperbolic kinetics were found for all substrates yielding Km values of about 10 mM for ammonium, 1 mM for 2-oxoglutarate and 0.1 mM for NADH in the direction of amination, and 10 mM for glutamate and 0.7 mM for NAD in the direction of deamination.
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PMID:Purification and properties of NAD-dependent glutamate dehydrogenase from Phycomyces spores. 322 Dec

The effect of hypoxia and post-hypoxic recovery were studied in gastrocnemius muscle of young-adult and mature beagle dogs. Furthermore, the possible interference of pharmacological treatment with nicergoline was evaluated in these conditions. Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose 6-phosphate, pyruvate, lactate), Kreb's cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate) and related free amino acids (glutamate, alanine), ammonium ion, energy store and mediators (ATP, ADP, AMP and creatine phosphate), and the energy charge potential were evaluated. Furthermore, in the crude extract and/or mitochondrial fraction of another portion of the same gastrocnemius muscle the maximum rate (Vmax) of some muscular enzymes related to the anaerobic glycolytic pathway (hexokinase, lactate dehydrogenase), the Kreb's cycle (citrate synthase, malate dehydrogenase), the aminoacid pool related to the Krebs' cycle (glutamate dehydrogenase and aspartate aminotransferase), the electron transfer chain (cytochrome oxidase) and NAD+/NADH exchanges (total NADH cytochrome c reductase) was evaluated. Some glycolytic metabolites and Krebs' cycle intermediates were modified by acute hypoxia, while free amino acids and energy mediators remained practically unchanged. The pharmacological treatment maintained the glucose and succinate muscular concentrations within the normal range, during hypoxia. The behaviour of muscular metabolites during hypoxia and/or post-hypoxic recovery is an age-related event. In fact, only in young-adult animals did the altered values return to normal in post-hypoxic recovery. In the present experimental conditions, only minor changes were observed as far as muscular enzyme activities are concerned. In any case, some enzyme activities tested showed different Vmax in young-adult dogs in comparison with mature ones.
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PMID:Effect of hypoxia, aging and pharmacological treatment on muscular metabolites and enzyme activities. 322 9

A rapid purification procedure for glutamate dehydrogenase (GDH) from Bacillus stearothermophilus var calidolactis was developed. The homogeneous enzyme with a total molecular weight of approximately 240,000 daltons, contained 6 identical subunits. No high molecular weight form of GDH present in crude extracts was found after elution of the enzyme from a 5'AMP-Sepharose column with 4 M urea. The purified enzyme functions in both directions i.e. amination and deamination and is strictly specific for NAD. 2-Oxo glutarate, glutamate or 2-mercaptoethanol protects against heat inactivation. NADH or ammonia, on the other hand, makes GDH more sensitive to heat. The purified enzyme undergoes thermal inactivation process.
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PMID:Thermophilic NAD-dependent glutamate dehydrogenase from Bacillus stearothermophilus. 403 15

1. Changes in the concentrations of ammonia, glutamine, glutamate, 2-oxoglutarate, 3-hydroxybutyrate, acetoacetate, alanine, aspartate, malate, lactate, pyruvate, NAD(+), NADH and adenine nucleotides were measured in freeze-clamped rat liver during ischaemia. 2. Although the concentrations of most of the metabolites changed rapidly during ischaemia the ratios [glutamate]/[2-oxoglutarate][NH(4) (+)] and [3-hydroxybutyrate]/[acetoacetate] changed equally and the value of the expression [3-hydroxybutyrate][2-oxoglutarate][NH(4) (+)]/[acetoacetate][glutamate] remained approximately constant, indicating that the 3-hydroxybutyrate dehydrogenase and glutamate dehydrogenase systems were at near-equilibrium with the mitochondrial NAD(+) couple. 3. The value of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] was about 0.7 in vivo and remained fairly constant during the ischaemic period of 5min, although the concentrations of alanine and oxoglutarate changed substantially. No explanation can be offered why the value of the ratio differed from that of the equilibrium constant of the alanine aminotransferase reaction, which is 1.48. 4. Injection of l-cycloserine 60min before the rats were killed increased the concentration of alanine in the liver fourfold and decreased the concentration of the other metabolites measured, except that of pyruvate. During ischaemia the concentration of alanine did not change but that of aspartate almost doubled. 5. After treatment with l-cycloserine the value in vivo of the expression [alanine][oxoglutarate]/[pyruvate][glutamate] rose from 0.7 to 2.4. During ischaemia the value returned to 0.8. 6. The effects of l-cycloserine are consistent with the assumption that it specifically inhibits alanine aminotransferase. 7. Most of the alanine formed during ischaemia is probably derived from pyruvate and from ammonia released by the deamination of adenine nucleotides and glutamine. The alanine is presumably formed by the combined action of glutamate dehydrogenase and alanine aminotransferase. 8. The rate of anaerobic glycolysis, calculated from the increase in the lactate concentration, was 1.3mumol/min per g fresh wt. 9. Although the concentrations of the adenine nucleotides changed rapidly during ischaemia, the ratio [ATP][AMP]/[ADP](2) remained constant at 0.54, indicating that adenylate kinase established near-equilibrium under these conditions.
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PMID:Effects of ischaemia on metabolite concentrations in rat liver. 431 90

The effect of cAMP on the intracellular levels of five enzymes concerned with the interconversion of glutamate and glutamine in E. coli has been examined. Cyclic AMP added to the culture medium increases the levels of glutamate dehydrogenase (EC 1.4.1.4) and glutamine synthetase (EC 6.3.1.2); it decreases the levels of glutamate synthase (EC 1.4.1.X), and glutaminase A (EC 3.5.1.2). Cyclic AMP did not affect the level of glutaminase B (EC 3.5.1.2). These alterations in enzyme levels by cAMP require cyclic AMP receptor protein, since the levels of these enzymes were unchanged by cAMP in a mutant lacking this receptor. Chloramphenicol also abolished the effects of cAMP, a result that implies protein synthesis is necessary for these changes in enzyme levels to occur. The reciprocal effects of cAMP on the levels of these enzymes may play an important role in the cellular regulation of nitrogen metabolism.
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PMID:Adenosine 3':5'-cyclic monophosphate control of the enzymes of glutamine metabolism in Escherichia coli. 440 45


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