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

---

Query: EC:1.4.1.2 (glutamate dehydrogenase)
4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Experiments were designed to examine the early events in the initiation of glutamate deamination in kidney. Perfused kidneys from methionine sulfoximine-treated rats formed ammonia from [15N]glutamate via the purine nucleotide cycle. The turnover of the 6-amino group of adenine nucleotides to yield ammonia occurred at the rate of 0.30 mumol/g of kidney/min. This rate is 3-4 times larger than in liver and is in agreement with published rates of the purine nucleotide cycle in kidney. The addition of 0.1 mM fluorocitrate to glutamate perfusions stimulated ammonia formation 3 1/2-fold. The turnover of the 6-amino group of adenine nucleotides increased during the first 5 min after adding fluorocitrate to form ammonia predominately from tissue glutamate and aspartate. This turnover correlates with a 3 1/2-fold increase in kidney tissue IMP levels. As the ATP/ADP ratio fell the purine nucleotide cycle was inhibited and glutamate dehydrogenase was stimulated to form ammonia stoichiometric with glutamate taken up from the perfusate. Ammonia formation via glutamate dehydrogenase occurred at a rate of 1.0 mumol/g of kidney/min. Fluorocitrate completely blocked ammonia formation from aspartate in perfusions. The perfused kidney formed ammonia from aspartate via the purine nucleotide cycle at a rate of 1.0 mumol/g of kidney/min. The results indicate a discrete role for aspartate in renal metabolism. Ammonia formation via the purine nucleotide cycle can occur at significant rates and equal to the rate of ammonia formation from glutamate via glutamate dehydrogenase.
...
PMID:Early events in the initiation of ammonia formation in kidney. 613 Oct 71

The enzymes of glutamate metabolism were estimated in astrocytes isolated from brains of normal rats and those injected with the potent convulsant, methionine sulfoximine (MSO), which inhibits glutamine synthetase and induces Alzheimer type II astrocytosis. The wet weight, dry weight; contents of DNA, RNA, protein and the activities of glutamate dehydrogenase and aspartate aminotransferase were elevated following MSO administration. The metabolic effects of MSO were found to be different from those of ammonia wherein a fall in the activity of glutamate dehydrogenase and an increase in the activity of glutamine synthetase was noticed. Based on these results it is suggested that there might be an inverse relationship in the functioning of these two enzymes. Such a relationship would help in preventing the depletion of energy pools in a given cellular compartment during ammonia detoxification.
...
PMID:Effects of methionine sulfoximine on the enzymes of glutamate metabolism in isolated astrocytes of rat brain. 614 Sep 23

Enzymes of glutamate metabolism were studied in synaptosomes prepared from normal rats and those treated with acute (300 mg/kg) and subacute (150 mg/kg) doses of the convulsant methionine sulfoximine (MSO). The activities of glutamine synthetase, glutamate dehydrogenase and aspartate aminotransferase were inhibited in the synaptosomes of drug treated animals. It is suggested that MSO would suppress the formation of glutamine and glutamate and consequently the releasable pool of glutamate, aspartate and GABA. These neurotransmitters would be depleted from the nerve endings. It is also indicated that the ammonia accumulated would affect the cerebral functioning by interfering with the maintenance of ionic gradients.
...
PMID:Suppression of the enzymes of glutamate metabolism in cortical synaptosomes in methionine sulfoximine toxicity. 614 87

The cytosolic precursor for the mitochondrial glutamate dehydrogenase of rat liver was synthesized in a cell-free reticulocyte lysate using messenger RNA from rat liver. To check whether this precursor had enzymatic activity, a highly sensitive fluorimetric method, which can measure picogram quantities of enzyme, was used together with competitive dissociation of the precursor from an immunoprecipitate with inactive glutamate dehydrogenase. Glutamate dehydrogenase activity, corresponding to that estimated from incorporation of [35S]-methionine, was detected in the precursor. The significance of this finding is discussed.
...
PMID:The precursor of rat liver mitochondrial glutamate dehydrogenase has enzymatic activity. 686 47

Although glutamate is a key compound in nitrogen metabolism, little is known about the function or regulation of its two biosynthetic enzymes, glutamate dehydrogenase and glutamate synthase. To begin the characterization of glutamate formation in Salmonella typhimurium, we isolated mutants having altered glutamate dehydrogenase and glutamate synthase activities. Mutants which failed to grow on media with glucose as the carbon source and less than 1 mM (NH(4))(2)SO(4) as the nitrogen source (Asm(-)) had about one-fourth the normal glutamate synthase activity and one-half the glutamine synthetase activity. The asm mutations also prevented growth with alanine, arginine, or proline as nitrogen sources and conferred resistance to methionine sulfoximine. When a mutation (gdh-51) causing the loss of glutamate dehydrogenase activity was transferred into a strain with an asm-102 mutation, the resulting asm-102 gdh-51 mutant had a partial requirement for glutamate. A strain isolated as a complete glutamate auxotroph had a third mutation, in addition to the asm-102 gdh-51 lesions, that further decreased the glutamate synthase activities to 1/20 the normal level. Both the asm-102 and gdh-51 mutations were located on the S. typhimurium linkage map at sites distinct from those found for mutations causing similar phenotypes in Klebsiella aerogenes and Escherichia coli.
...
PMID:Salmonella typhimurium mutants with altered glutamate dehydrogenase and glutamate synthase activities. 698 57

1. The metabolism of L-alanine was studied in isolated guinea-pig kidney-cortex tubules. 2. In contrast with previous conclusions of Krebs [(1935) Biochem. J. 29, 1951-1969], glutamine was found to be the main carbon and nitrogenous product of the metabolism of alanine (at 1 and 5 mM). Glutamate and ammonia were only minor products. 3. At neither concentration of alanine was there accumulation of glucose, glycogen, pyruvate, lactate, aspartate or tricarboxylic acid-cycle intermediates. 4. Carbon-balance calculations and the release of 14CO2 from [U-14C]alanine indicate that oxidation of the alanine carbon skeleton occurred at both substrate concentrations. 5. A pathway involving alanine aminotransferase, glutamate dehydrogenase, glutamine synthetase, pyruvate dehydrogenase, pyruvate carboxylase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of alanine into glutamine. 6. Strong evidence for this pathway was obtained by: (i) suppressing alanine removal by amino-oxyacetate, and inhibitor of transaminases, (ii) measuring the release of 14CO2 from [1-14C]alanine, (iii) the use of L-methionine DL-sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from alanine, and (iv) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from alanine. 7. In this pathway, the central role of pyruvate carboxylase, which explains the discrepancy between our results and those of Krebs (1935), was also demonstrated.
...
PMID:The conversion of alanine into glutamine in guinea-pig renal cortex. Essential role of pyruvate carboxylase. 733 38

1. The pathways and the fate of glutamate carbon and nitrogen were investigated in isolated guinea-pig kidney-cortex tubules. 2. At low glutamate concentration (1 mM), the glutamate carbon skeleton was either completely oxidized or converted into glutamine. At high glutamate concentration (5 mM), glucose, lactate and alanine were additional products of glutamate metabolism. 3. At neither concentration of glutamate was there accumulation of ammonia. 4. Nitrogen-balance calculations and the release of 14CO2 from L-[1-14C]glutamate (which gives an estimation of the flux of glutamate carbon skeleton through alpha-oxoglutarate dehydrogenase) clearly indicated that, despite the absence of ammonia accumulation, glutamate metabolism was initiated by the action of glutamate dehydrogenase and not by transamination reactions as suggested by Klahr, Schoolwerth & Bourgoignie [(1972) Am. J. Physiol. 222, 813-820] and Preuss [(1972) Am. J. Physiol. 222, 1395-1397]. Additional evidence for this was obtained by the use of (i) amino-oxyacetate, an inhibitor of transaminases, which did not decrease glutamate removal, or (ii) L-methionine DL-sulphoximine, an inhibitor of glutamine synthetase, which caused an accumulation of ammonia from glutamate. 5. Addition of NH4Cl plus glutamate caused an increase in both glutamate removal and glutamine synthesis, demonstrating that the supply of ammonia via glutamate dehydrogenase is the rate-limiting step in glutamine formation from glutamate. NH4Cl also inhibited the flux of glutamate through glutamate dehydrogenase and the formation of glucose, alanine and lactate. 6. The activities of enzymes possibly involved in the glutamate conversion into pyruvate were measured in guinea-pig renal cortex. 7. Renal arteriovenous-difference measurements revealed that in vivo the guinea-pig kidney adds glutamine and alanine to the circulating blood.
...
PMID:Fate of glutamate carbon and nitrogen in isolated guinea-pig kidney-cortex tubules. Evidence for involvement of glutamate dehydrogenase in glutamine sythesis from glutamate. 747 41

Two residues, K89 and S380, thought to interact with the gamma-carboxyl group of the substrate L-glutamate, have been altered by site-directed mutagenesis of clostridial glutamate dehydrogenase (GDH). The single mutants K89L and S380V and the combined double mutant K89L/S380V were constructed. All three mutants were satisfactorily overproduced in soluble form. However, only the K89L mutant was retained by the dye column normally used in purifying the wild-type enzyme. All three mutant enzymes were purified to homogeneity and tested for substrate specificity with 24 amino acids. The single mutant S380V showed no detectable activity. The alternative single mutant K89L showed an activity towards L-glutamate that was decreased nearly 2000-fold compared with wild-type enzyme, whereas the activities towards the monocarboxylic substrates alpha-aminobutyrate and norvaline were increased 2- to 3-fold. A similar level of activity was obtained with methionine (0.005 U/mg) and norleucine (0.012 U/mg), neither of which give any activity with the wild-type enzyme under the same conditions. The double mutant showed decreased activity with all substrates compared with the wild-type GDH. In view of its novel activities, the K89L mutant was investigated in greater detail. A strictly linear relationship between reaction velocity and substrate concentration was observed up to 80 mM L-methionine and 200 mM L-norleucine, implying very high Km values. Values of kcat/Km for L-methionine and L-norleucine were 6.7 x 10(-2) and 0.15 s-1 M-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Alteration of the amino acid substrate specificity of clostridial glutamate dehydrogenase by site-directed mutagenesis of an active-site lysine residue. 763 Aug 85

The amphistomes Gigantocotyle explanatum and Gastrothylax crumenifer utilize leucine, alanine, proline and methionine during in vitro incubations. Autoradiography on sections of these flukes reveal a time-dependent differential incorporation of tritium-labelled amino acids in various tissues. The tegument appears to be the primary surface through which amino acids are absorbed. Following absorption, the reappearance of [3H]-leucine and [3H]-alanine on the tegumental surface during late chase periods indicates their possible involvement in tegumental secretion. A combination of diffusion and carrier-mediated uptake, possibly involving gamma-glutamyl transpeptidase, is indicated. The transport loci show differences in carrier-affinity (Kt) and maximum uptake velocities (Vmax) for amino acids under study, which suggest multiple transport molecules. Metabolic studies reveal that aspartate, alanine, ornithine, proline, leucine and methionine undergo transamination through 2-oxoglutarate-linked transaminases, distributed in the cytosolic and mitochondrial fractions of G. explanatum and G. crumenifer. With the exception of alanine transaminase, the enzyme levels in the cytosolic fraction were higher than the mitochondrial fraction of the two amphistomes. Predominantly cytosolic glutamate dehydrogenase which was comparatively higher in G. explanatum, catalyse amination of alpha-ketoglutarate. A high level of cytosolic arginase alone does not indicate a functional urea cycle. A tentative pathway of amino acid metabolism in these amphistomes is proposed.
...
PMID:[3H]-amino acid uptake and metabolic studies on Gigantocotyle explanatum and Gastrothylax crumenifer (Digenea: Paramphistomidae). 763 32

A completely defined growth medium has been developed to determine the nitrogen requirements for several species of ruminal bacteria, and has revealed two strains which are impaired in de novo biosynthesis of certain amino acids. Using NH4Cl as a sole nitrogen source, the medium supported growth of Butyrivibrio, Selenomonas, Prevotella and Streptococcus species. One strain of B. fibrisolvens (E14) and one strain of P. ruminicola (GA33) did not grow in the presence of NH4Cl until the medium was supplemented with amino acids or peptides. For B. fibrisolvens strain E14, methionine was identified as the specific growth-limiting amino acid although methionine alone did not support growth in the absence of NH4Cl. For P. ruminicola strain GA33, any individual amino acid other than methionine or cysteine could supplement the medium and support growth. Enzyme assays confirmed a lack of NADH and NADPH-dependent glutamate dehydrogenase (GDH) activities in this strain.
...
PMID:A defined medium for rumen bacteria and identification of strains impaired in de novo biosynthesis of certain amino acids. 763 95


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

---