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)

The effect of gentamicin on both glutamate synthesis and glutamate deamination was studied in kidney-cortex mitochondria and tubules isolated from both control and gentamicin-treated animals. In kidney-cortex mitochondria which were permeabilized in order to make a free access of substrates and antibiotic to the glutamate dehydrogenase, gentamicin appeared to be a very potent inhibitor of glutamate synthesis, resulting in about 60% decrease of the enzyme activity at 5 mM concentration. Other aminoglycoside antibiotics decreased the enzymatic activity, in the following order: gentamicin > neomycin = tobramycin = kanamycin > biodacyna > amikacin > streptomycin. This, in principle, corresponds to their known nephrotoxic potential observed in vivo. The inhibitory action of antibiotics was abolished by neither ADP nor leucine, allosteric activators of glutamate dehydrogenase. Surprisingly, gentamicin did not decrease the rate of ammonia formation from glutamate when added to both renal tubules and mitochondria isolated from control rabbits. This indicates that the antibiotic exerts its inhibitory effect on glutamate dehydrogenase activity in the direction of glutamate synthesis only. In contrast, the rate of both glutamate deamination and glutamate synthesis was about 40% lower in renal tubules and mitochondria isolated from kidney-cortex of animals which were given antibiotics for 10 days. In view of these results it seems that (i) the depression of ammoniagenesis in gentamicin-treated animals may be due to a decrease of glutamate dehydrogenase content and (ii) under conditions in vitro the aminoglycoside inhibits the enzyme activity in the direction of glutamate synthesis while it does not affect the glutamate deamination.
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PMID:Differential in vivo and in vitro effect of gentamicin on glutamate synthesis and glutamate deamination in rabbit kidney-cortex tubules and mitochondria. 136 90

The developmental changes of glutamate dehydrogenase activity in the fetal and neonatal rat liver were investigated, as well as the effects of branched-chain amino acids on this enzyme. Hepatic glutamate dehydrogenase activity showed a marked increase at the end of the fetal period and peaked on the 5th day of neonate at approximately 3 times higher than the adult level. Glutamate dehydrogenase was activated by leucine, isoleucine, and valine in this order when they were added to isolated intact liver mitochondria in vitro. The enhancement of enzyme activity was more marked in fetal rats than in adults. In contrast, when branched-chain amino acids were added after disrupting the mitochondrial membrane by sonication, only leucine slightly activated glutamate dehydrogenase, while isoleucine and valine slightly inhibited its activity. Our findings suggest that glutamate may be actively synthesized in the developing rat liver mitochondria and then transaminated to other nonessential amino acids for protein synthesis, and that increased intramitochondrial branched-chain amino acid concentrations may enhance glutamate dehydrogenase activity. This anabolic metabolism will contribute to the fetal growth and development.
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PMID:Developmental changes of glutamate dehydrogenase activity in rat liver mitochondria and its enhancement by branched-chain amino acids. 142 Jun 17

Affinity labeling studies of NADP(+)-glutamate dehydrogenase from Salmonella typhimurium have shown that the peptide Leu-282-Lys-286 is located near the coenzyme site [Haeffner-Gormley et al. (1991) J. Biol. Chem. 266, 5388-5394]. The present study was undertaken to evaluate the role of lysine-286. The mutant enzymes K286R, K286Q, and K286E were prepared by site-directed mutagenesis, expressed in Escherichia coli, and purified. The Vmax values (micromoles of NADPH per minute per milligram of protein) were similar for WT (270), K286R (529), K296Q (409), and K286E (382) enzymes. As measured at pH 7.9, the Km value for NADPH was much greater for K286E (280 microM) than for WT (9.8 microM), K286R (30 microM), or K286Q (66 microM) enzymes. The efficiencies (kcat/Km) of the WT and K286R mutant were similar (1.2 x 10(3) min-1 microM-1 and 1.0 x 10(3) min-1 microM-1, respectively) while those of K286Q (0.30 x 10(3) min-1 microM-1) and K286E (0.07 x 10(3) min-1 microM-1) were greatly reduced. The decreased efficiency of the K286E mutant results from the increase in Km-NADPH, consistent with a role for a basic residue at position 286 which enhances the binding of NADPH. Plots of Vmax vs pH showed the pH optima to be 8.1-8.3 for all enzymes at saturating NADPH concentrations. A 40-fold increase in Km-NADPH for K286E was observed as the pH increased from 5.98 to 8.08, from which a unique pKe of 6.5 was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Importance of lysine-286 at the NADP site of glutamate dehydrogenase from Salmonella typhimurium. 151 Sep 67

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.
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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.
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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

One hundred and one young-adult female Sprague-Dawley rats were acclimatized to metabolic cages for 2 days. After that time 24-hour urine was collected at a constant cooling temperature of 0-4 degrees C. After gel filtration the enzyme activities were determined, and the resulting values were used to calculate 24-hour excretions. The following reference ranges (2.5 and 97.5 percentiles) were determined (in mU/24 h): lactate dehydrogenase 43-181; phosphohexoseisomerase 45-1445; glutathione-S-transferase 1-299; alkaline phosphatase 27-1239; leucine arylamidase 72-377; gamma-glutamyltransferase 1334-9188; arylsulphatase A 59-309; beta-galactosidase 76-305; beta-glucuronidase 20-2756; beta-N-acetyl-D-glucosaminidase 66-491; glutamate dehydrogenase 7-711. There was a significant (though not very high) correlation with diuresis for the lysosomal enzymes beta-N-acetyl-D-glucosaminidase, arylsulphatase A and beta-galactosidase, and for glutamate dehydrogenase, lactate dehydrogenase, phosphohexoseisomerase and alkaline phosphatase. The relation to creatinine excretion was markedly close for the lysosomal enzymes beta-N-acetyl-D-glucosaminidase, arylsulphatase A and beta-galactosidase (r = 0.71-0.83), as well as for alkaline phosphatase, leucine arylamidase and gamma-glutamyltransferase. There was a relatively high correlation between the excretion of beta-N-acetyl-D-glucosaminidase, arylsulphatase A and beta-galactosidase among themselves (r = 0.63-0.81) as well as between leucine arylamidase and gamma-glutamyltransferase (r = 0.75).
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PMID:Excretion of urinary enzymes in female Sprague-Dawley rats in relation to cellular compartment, creatinine excretion and diuresis. 179 3

Leucine and beta-(+/-)-2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (BCH) stimulated, in a dose-dependent manner, reductive amination of 2-oxoglutarate in rat brain synaptosomes treated with Triton X-100. The concentration dependence curves were sigmoid, with 10-15-fold stimulations at 15 mM leucine (or BCH); oxidative deamination of glutamate also was enhanced, albeit less. In intact synaptosomes, leucine and BCH elevated oxygen uptake and increased ammonia formation, consistent with stimulation of glutamate dehydrogenase (GDH). Enhancement of oxidative deamination was seen with endogenous as well as exogenous glutamate and with glutamate generated inside synaptosomes from added glutamine. With endogenous glutamate, the stimulation of oxidative deamination was accompanied by a decrease in aspartate formation, which suggests a concomitant reduction in flux through aspartate aminotransferase. Activation of reductive amination of 2-oxoglutarate by BCH or leucine could not be demonstrated even in synaptosomes depleted of internal glutamate. It is suggested that GDH in synaptosomes functions in the direction of glutamate oxidation, and that leucine may act as an endogenous activator of GDH in brain in vivo.
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PMID:Activation of glutamate dehydrogenase by leucine and its nonmetabolizable analogue in rat brain synaptosomes. 196 60

Cerebral activities of glutamate dehydrogenase (GDH), glutamine synthetase (GS), and branched-chain amino acid aminotransferase (BCAA-T) along with the levels of ammonia in serum and brain were determined in normal, sham-operated and partially hepatectomized rats. Mild hyperammonemia was observed in sham-operated animals, and the cerebral activities of all the enzymes studied were found to be decreased when compared with those of normal animals. In hepatectomized animals, blood and brain ammonia levels were elevated further. In these animals, GS activity returned to the normal values and that of BCCA-T was elevated, while there was a continued suppression of GDH activity. These results were discussed in relation to the utilization of BCAA (leucine, isoleucine, and valine) for the synthesis of glutamate and glutamine in brain in hyperammonemic states.
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PMID:Effects of partial hepatectomy on the enzymes of cerebral glutamate and branched-chain amino acid metabolism. 197 Feb 45

Much evidence has accumulated to support the idea that leucine can stimulate insulin release by allosterically activating glutamate dehydrogenase thus enhancing glutamate metabolism. It is less clear how the metabolism of leucine itself contributes to the signal for insulin release. We recently found that culturing pancreatic islets for 1 day at low glucose (1 mM) suppressed glucose-induced insulin release, but preserved leucine-induced insulin release. When islets were cultured at high glucose (20 mM), glucose-induced insulin release was preserved, but leucine-induced insulin release was suppressed (MacDonald, M. J., Fahien, L. A., McKenzie, D. I., and Moran, S. M. (1990) Am. J. Physiol., 259, E548-E554). The suppression of leucine-induced insulin release can be explained by glucose's suppression of the synthesis of the enzyme that catalyzes the first committed step of leucine metabolism, branched chain ketoacid dehydrogenase complex (BCKDH). High glucose suppressed the enzyme activity of the E1 component of the BCKDH complex, as well as the total activity of the BCKDH complex, to usually negligible levels in islets and decreased by an average of 90% the mRNA which encodes E1 alpha, the catalytic subunit of the E1 component of BCKDH, in islets and rat insulinoma cells. Time course studies showed that about 24 h in culture was required to maximally induce or suppress the expression of BCKDH E1 alpha. Culture at high glutamine with or without leucine mimicked to a lesser and more variable degree the effects of high glucose on leucine-induced insulin release and BCKDH E1 alpha mRNA. Leucine-plus-glutamine-induced insulin release was present after culture of islets with glucose and with or without any other secretagogue. Also, glutamate dehydrogenase transcripts and enzyme activity were not significantly altered by varying the concentration of glucose in the culture medium. Thus, leucine's insulinotropism via activation of glutamate dehydrogenase is constitutive. Preproinsulin mRNA levels were markedly increased at high glucose and glyceraldehyde phosphate dehydrogenase transcripts were either unaffected or slightly increased by glucose. Glutamine did not significantly effect the expression of genes other than BCKDH E1 alpha, and leucine had little or no effect on the expression of any of the four genes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Glucose regulates leucine-induced insulin release and the expression of the branched chain ketoacid dehydrogenase E1 alpha subunit gene in pancreatic islets. 198 51

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


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