Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.4.1.4 (glutamate dehydrogenase)
 4,358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of subacute and acute doses of ammonium acetate was studied on the production of 14CO2 from 14C-labeled glutamate and aspartate by neuronal perikarya and synaptosomes isolated from rat cerebellum. Studies with inhibitors for aminotransferases (aminooxy acetic acid) and glutamate dehydrogenase (glutamic acid diethyl ester) indicated that transamination reactions play a major role in this process. There was a suppression in this process in hyperammonemic states. Activities of the enzymes, aspartate aminotransferase, alanine aminotransferase, glutamate dehydrogenase and glutaminase were decreased in both preparations in hyperammonemic states. Activity of glutamine synthetase was unaltered.
 ...
PMID:Ammonia-induced alterations in the metabolism of glutamate and aspartate in neuronal perikarya and synaptosomes of rat cerebellum. 135 57

Pathophysiological concentrations of ammonia, both in vivo and in vitro, suppressed the production of 14CO2 from 14C-labelled glutamate and aspartate in astrocytes isolated from the rat cerebellum. Suppression of 14CO2 production with (aminooxy)acetic acid but not with glutamic acid diethyl ester indicated that transamination plays a major role in the oxidation of glutamate carbons. Activities of the enzymes, aspartate amino-transferase, alanine aminotransferase and glutaminase were decreased while those of glutamate dehydrogenase and glutamine synthetase were enhanced in the cerebellar astrocytes during hyperammonemic states. These results suggest an impairment of astrocytic glutamate metabolism during hyperammonemia.
 ...
PMID:Hyperammonemic alterations in the metabolism of glutamate and aspartate in rat cerebellar astrocytes. 135 96

A simple procedure for the measurement of gamma-glutamyl hydrolase (conjugase) activity is described. Glutamic acid released from pteroylpenta-gamma-glutamate by hog kidney and chicken pancreas conjugases was quantitated using the dye 4,4'-bis(dimethylamino)benzophenone hydrazone. The procedure involves hydrolysis of the folylpoly-gamma-glutamate substrate by conjugase, conversion of glutamate to alpha-ketoglutarate by L-glutamate dehydrogenase and colorimetric measurement of the BDBH derivative of alpha-ketoglutarate. The release of as little as one nmol of glutamic acid from the substrate can be measured by this procedure, which is well suited for the assay of a variety of conjugase preparations. In addition, the method should provide a general assay for the enzymatic hydrolysis of various folate and antifolate polyglutamates.
 ...
PMID:A rapid colorimetric assay for gamma-glutamyl hydrolase (conjugase). 136 32

The distribution of amino acids between plasma, liver and brain was studied in adult male rats, fed a diet containing 8.7, 17 (control animals), 32 and 51% of protein during 15 days. The caloric intake was nearly equal in all groups. The highest food intake was observed in the animals on the low protein diet. Changes in plasma amino acids were variable. In contrast to the behavior of most amino acids in plasma, the branched chain amino acids were highest in the animals fed the 51% protein diet. Despite the low protein intake in the animals fed a 8.7% protein diet, the concentration of serine, glutamic acid, glutamine, glycine, alanine, methionine, isoleucine, leucine, phenylalanine and ornithine were significantly higher compared to control animals, whereas in those receiving a high protein diet, valine, leucine, tyrosine, tryptophan and histidine increased in relation to the increased protein and amino acid intake. The plasma amino acid patterns are not greatly influenced by the amino acid distribution in the food and the amount ingested. Alanine aminotransferase, aspartate aminotransferase, glutamate dehydrogenase and cholinesterase showed a two- to fivefold increased activity in the liver of animals consuming a high protein diet. In the brain, the concentration of valine, leucine, isoleucine, phenylalanine and tyrosine in animals receiving the low protein diet was higher than in controls and increased further with increasing protein content of the diet. Glutamine was increased in all dietary groups. The predicted influx of amino acids showed increasing influx rates in dependence of the plasma amino acid concentration. The entry of tyrosine and tryptophan and their brain concentration was inversely proportional to the protein content of the diet. In the present study which considers long-term adaptation to an increasing protein and amino acid intake in comparison to a balanced control protein diet, the levels of the indispensable amino acids were maintained within narrow limits in the brain and liver. The results indicate that inspite of a variable protein intake, the body tends to keep organ amino acids in relatively narrow limits favoring in this way amino acid homeostasis.
 ...
PMID:Effect of different protein diets on the distribution of amino acids in plasma, liver and brain in the rat. 159 Jun 69

NADP(+)-specific glutamate dehydrogenase of Salmonella typhimurium was previously shown to react irreversibly at the coenzyme site with the nucleotide analogue 2-((4-bromo-2,3-dioxobutyl)thio)-1,N6-ethenoadenosine 2',5'-bisphosphate (2-BDB-T epsilon A 2',5'-DP) yielding a partially active enzyme, and inactivation was attributed to modification of the peptide Leu282-Cys-Glu-Ile-Lys286 (Bansal, A., Dayton, M.A., Zalkin, H., and Colman, R.F. (1989) J. Biol. Chem. 264, 9827-9835). Three mutant enzymes have now been engineered, expressed in Escherichia coli, and purified: the single mutants C283I and E284Q and the double mutant C283I:E284Q. The wild-type and mutant enzymes have similar specific activities and Km values for alpha-ketoglutarate, ammonium ion, and NADPH, indicating that neither cysteine 283 nor glutamic acid 284 is essential for activity. The mutant enzyme E284Q, like wild-type glutamate dehydrogenase, is substantially inactivated by 2-BDB-T epsilon A 2',5'-DP. In contrast, the two cysteine mutant enzymes, C283I and C283I:E284Q, are not inactivated by 2-BDB-T epsilon A 2',5'-DP. Modified tryptic peptides with the sequence Leu-X-Glu(Gln)-Ile-Lys were isolated from wild-type or E284Q enzymes inactivated by 2-BDB-T epsilon A 2',5'-DP. This peptide was absent from digests of active wild-type enzyme modified in the presence of the protectant NADPH and from digests of active C283I enzyme after incubation with 2-BDB-T epsilon A 2',5'-DP. Although it is not required for catalytic activity, cysteine 283 is implicated by the results of the affinity labeling experiments as the reaction target of the nucleotide analogue and is located in the region of the coenzyme binding site.
 ...
PMID:Evaluation of cysteine 283 and glutamic acid 284 in the coenzyme binding site of Salmonella typhimurium glutamate dehydrogenase by site-directed mutagenesis and reaction with the nucleotide analogue 2-[4-bromo-2,3-dioxobutyl)thio)-1,N6-ethenoadenosine 2',5'-bisphosphate. 167 12

An enzymatic method for the determination of free glutamic acid in meat products and dried soups was collaboratively studied in 11 laboratories. In the presence of the enzyme glutamate dehydrogenase, L-glutamic acid is oxidatively deaminated by nicotinamide adenine dinucleotide (NAD) to 2-oxoglutarate. In a reaction catalyzed by diaphorase, the NADH thus formed converts 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride to a formazan, which is measured in the visible range at 492 nm. Fourteen samples (7 samples of minced sausage and 7 samples of dried cauliflower soup) with glutamate contents varying between 0.4 and 16 g/kg were included in the study. Materials were distributed to participants as blind duplicates and as split level pairs. The mean relative standard deviation (RSDR) for reproducibility for the dried soup material containing glutamate between 7 and 16 g/kg was 4.6%. RSDR values for samples of minced sausage containing glutamate at lower levels (0.4-1.3 g/kg) were between 12 and 16%.
 ...
PMID:Enzymatic determination of free glutamic acid in dried soups and in minced sausages: NMKL collaborative study. 168 80

We measured biochemical markers of excitability in brain excised for neurosurgical therapy of epilepsy. Intraoperative electrocorticography was used to identify and compare samples from regions of persistent interictal spike discharges and areas of the cerebral convexity which were free of interictal spiking. We found that interictal spiking was associated with elevated tissue levels of the excitatory amino acids glutamic acid (26%, p less than 0.001) and aspartic acid (25%, p less than 0.05). There was also a significant increase in the activity of the enzymes glutamic acid dehydrogenase (20%, p less than 0.01) and aspartate acid aminotransferase (18%, p less than 0.01) which are involved in their formation. There was no change in the levels of the inhibitory neurotransmitters GABA or taurine. We also found a significant increase in the activity of tyrosine hydroxylase (52%, p less than 0.001), the rate controlling enzyme in catecholamine biosynthesis. There was a reduction in the density (Bmax) of cortical alpha-1 adrenoceptors (26%, p less than 0.01) and a concomitant diminution of receptor coupled phosphatidylinositide metabolism (21%, p less than 0.01). This blunting of inhibitory noradrenergic transmembrane signaling may contribute to a relative imbalance between excitatory and inhibitory mechanisms in epileptogenic neocortex.
 ...
PMID:Biochemical markers of excitability in human neocortex. 177 85

An incubation medium was established for the microphotometric demonstration of glutamate dehydrogenase (Gldh) in cryostat sections of the rat hippocampus which served as an exemplary brain region. The final incubation medium consisted of 100 mM L-glutamic acid monosodium salt, 5 mM NAD, 10 mM sodium azide (NaN3), 5 mM ADP, 20 mM sodium chloride, 0.15 mM phenazine methosulfate (PMS), 5 mM nitroblue tetrazolium chloride and 22% polyvinyl alcohol (PVA) in 0.05 M Hepes buffer; the final pH was 7.5. The study showed that in the histochemical demonstration of Gldh the use of relatively high PVA concentrations were necessary to avoid diffusion artefacts because Gldh seems to be only loosely bound to the mitochondrial matrix. The use of NaN3 as a blocker of the respiratory chain was indispensible, because without NaN3 most reduction equivalents were lost through the respiratory chain. With PMS as an exogenous electron carrier, the demonstrable Gldh activities increased significantly indicating that, in the case of Gldh, the endogenous NADH tetrazolium reductase was not sufficiently effective. Furthermore, it was shown that Gldh was affected by many small molecules (e.g. activation by sodium ions, inhibition by magnesium and calcium ions) so that minor variations of the incubation conditions may cause major differences in demonstrable activities.
 ...
PMID:Microphotometric determination of enzymes in brain sections. III. Glutamate dehydrogenase. 233 53

Pathways of ammonia assimilation into glutamic acid were investigated in ammonia-grown and N2-fixing Clostridium kluyverii and Clostridium butyricum by measuring the specific activities of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. C. kluyverii had NADPH-glutamate dehydrogenase with a Km of 12.0 mM for NH4+. The glutamate dehydrogenase pathway played an important role in ammonia assimilation in ammonia-grown cells but was found to play a minor role relative to that of the glutamine synthetase/NADPH-glutamate synthase pathway in nitrogen-fixing cells when the intracellular NH4+ concentration and the low affinity of the enzyme for NH4+ were taken into account. In C. butyricum grown on glucose-salt medium with ammonia or N2 as the nitrogen source, glutamate dehydrogenase activity was undetectable, and the glutamine synthetase/NADH-glutamate synthase pathway was the predominant pathway of ammonia assimilation. Under these growth conditions, C. butyricum also lacked the activity of glucose-6-phosphate dehydrogenase, which catalyzes the regeneration of NADPH from NADP+. However, high activities of glucose-6-phosphate dehydrogenase as well as of NADPH-glutamate dehydrogenase with a Km of 2.8 mM for NH4+ were present in C. butyricum after growth on complex nitrogen and carbon sources. The ammonia-assimilating pathway of N2-fixing C. butyricum, which differs from that of the previously studied Bacillus polymyxa and Bacillus macerans, is discussed in relation to possible effects of the availability of ATP and of NADPH on ammonia-assimilating pathways.
 ...
PMID:Ammonia assimilation pathways in nitrogen-fixing Clostridium kluyverii and Clostridium butyricum. 256 48

A method for the quantitation of L-glutamic acid in the picomole range was developed by finding conditions which allowed the production of NADH by the action of the L-glutamate dehydrogenase (EC 1.4.1.3) and its subsequent transformation to a highly fluorescent derivative. The method measures linearly glutamate from 250 pmol to 5 nmol. For its simplicity and low cost it is ideally suited to the assay of a large number of samples within a single working day. Its application to the determination of regional glutamate levels in the rat brain, as well as to the measurement of ornithine aminotransferase (EC 2.6.1.13) activity from several tissues is described. The results are similar to those obtained by different methodologies in several laboratories, but the present method offers additional advantages.
 ...
PMID:A glutamate dehydrogenase-based method for the assay of L-glutamic acid: formation of pyridine nucleotide fluorescent derivatives. 257 90


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>