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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)

Using the semi-continuous cultivation technique we could establish that specifically in Streptomyces noursei JA 3890b during growth on a medium supplied with D,L-alanine, NH4+, and maize starch there are two different phenotypes of the organism and stationary states of metabolism, respectively. The expression of either the metabolic state I with an enhanced capacity to oxidative deamination of alanine via the NAD+-dependent alanaine dehydrogenase or the metabolic state 2 which may be characterized by the preferred use of ammonium ions via the NADP+-dependent glutamate dehydrogenase was shown to depend strongly on the conditions of inoculum cultivation. When the amino acid permeases were derepressed by cultivating the inoculum cells on amino acid media, probably due to the defective mechanism of negative feedback control of amino acid influx in this strain an abnormously high uptake of alanine was observed that, consequently, was correlated to the enhanced oxidation of this amino acid as well as to the intensive production of ammonia within the cell. This overproduction of cellular NH4+ seems to bring about the subsequent repression of biosynthetic glutamate dehydrogenase and so on the accumulation of ammonia autocatalytically may rise up (metabolic state I). On the other hand, if the influx of alanine was kept low and the NADH oxidation was less efficient, respectively, or when there was high cellular activity of glutamate dehydrogenase the level of ammonia never did exceed the respressory limit and, accordingly, the expression of the metabolic state 2 was observed. Switching-over of metabolic flux from the state 2 towards the state 1 can be brought about either by increasing the level of nitrogen sources in the medium or by adding buffers pH greater than 7.5. In contrast, decrease of cellular level of NH4+ was shown to induce the transition of metabolic state 1 into the state 2. This can be achieved not only by limitation of nitrogen source but also by adding different aminobenzoic acids and, alternatively, effectors of membrane function (short-chain alcohols), inhibitors of cytochrome oxidases (sodium azide, potassium cyanide), heavy metal (Fe++)-chelating agents (catechol, 2,5'-dipyridyl, o-phenanthroline), beta-alanine, and buffers pH less than 7. This suggests that these effectors are capable of preventing the abnormously high influx of amino acids as well as its wasteful catabolism within the cell of S. noursei JA 3890b. Therefore, it seems likely that by this way the aminobenzoic acids and similar effectors can diminish the catabolite repression or inhibition of secondary metabolism by cellular excess of some nitrogen compounds in good agreement with its well-known stimulatory action on the biosynthesis of the antibiotic nourseothricin in this strain.
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PMID:Regulative influence of o-aminobenzoic acid on the biosynthesis of nourseothricin in cultures of Streptomyces noursei JA 3890b. IV. Bistability of metabolism and the mechanism of action of aminobenzoic acids. 23 65

Glutamate dehydrogenase (L-glutamate:NADP+ oxidoreductase [deaminating], EC 1.4.1.4) has been purified from Escherichia coli B/r. The purity of the enzyme preparation has been established by polyacrylamide gel electrophoresis, ultracentrifugation, and gel filtration. A molecular weight of 300,000 +/- 20,000 has been calculated for the enzyme from sedimentation equilibrium measurements. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate and sedimentation equilibrium measurements in guanidine hydrochloride have revealed that glutamate dehydrogenase consists of polypeptide chains with the identical molecular weight of 50,000 +/- 5,000. The results of molecular weight determination lead us to propose that glutamate dehydrogenase is a hexamer of subunits with identical molecular weight. We also have studied the stability and kinetics of purified glutamate dehydrogenase. The enzyme remains active when heat treated or when left at room temperature for several months but is inactivated by freezing. The Michaelis constants of glutamate dehydrogenase are 1,100,640, and 40 muM for ammonia, 2-oxoglutarate, and reduced nicotinamide adenine dinucleotide phosphate, respectively.
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PMID:Glutamate dehydrogenase from Escherichia coli: purification and properties. 24 44

Isolated membrane fractions of Escherichia coli K-12 yielded complex immunoprecipitate patterns when Triton X-100 and sodium dodecyl sulfate extracts were examined by crossed immunoelectrophoresis with antienvelope immunoglobulins. Twelve of the 46 antigens in the immunoprecipitate patterns of inner (plasma) membranes were identified by zymograms and/or by the use of specific antisera. The following enzyme activities were detected in immunoprecipitates: 6-phosphogluconate dehydrogenase (EC 1.1.1.43); adenosine triphosphatase (EC 3.6.1.3); glutamate dehydrogenase (EC 1.4.1.4), two separate components; malate dehydrogenase (EC 1.1.1.37); dihydroorotate dehydrogenase (EC 1.3.3.1); succinate dehydrogenase (EC 1.3.99.1); lactate dehydrogeanse (EC 1.1.1.27); reduced nicotinamide adenine dinucleotide dehydrogenase (EC 1.6.99.3); protease (EC 3.4.21.1); and glycerol 3-phosphate dehydrogenase (EC 1.1.99.5). The corresponding immunoprecipitate pattern for isolated outer membranes consisted of at least 25 discrete antigens and differed strikingly from that obtained with inner membranes. Two major immunogens were identified as lipopolysaccharide and Braun lipoprotein. A protease-active immunoprecipitate was also detected in this fraction, but attempts to identify the Rosenbusch matrix protein in the crossed immunoelectrophoretic profile were unsuccessful.
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PMID:Immunochemical analysis of inner and outer membranes of Escherichia coli by crossed immunoelectrophoresis. 33 83

Six strains of Rickettsia prowazekii, two derived from human infections and four isolated from flying squirrels, two strains of R. typhi, and the single available strain of R. canada, were characterized by several biochemical procedures. The electrophoretic patterns on polyacrylamide gels of rickettsial proteins solubilized by sodium dodecyl sulfate revealed several species differences, but strains of the same species appeared to have identical patterns. Cytoplasmic fractions of the rickettsiae were examined for enzymatic activities and for polyacrylamide gel isoelectric focusing patterns. Some species differences were encountered in the activities or ratios of activities of glutamate-oxaloacetate transaminase, glutamate dehydrogenase, and malate dehydrogenase. When polyacrylamide gels were stained for malate dehydrogenase after electrophoresis, a single band became apparent with single extracts or mixtures of two strains of R. prowazekii, but two bands were seen with mixtures of a strain of R. prowazekii and one of R. typhi. The isoelectric focusing patterns of the soluble proteins revealed numerous species differences, especially between R. canada and the other two species, and a few differences among the strains of R. prowazekii. The patterns of the two human strains, Breinl and E(R), differed in at least one location, and both differed from the flying squirrel strains in the displacement of one band. One of the flying squirrel strains, GvF-16, contained a protein band not seen in the other five strains. Despite these minor differences, a striking similarity was revealed by all the biochemical tests performed between the R. prowazekii strains of human and flying squirrel origin.
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PMID:Biochemical characteristics of typhus group rickettsiae with special attention to the Rickettsia prowazekii strains isolated from flying squirrels. 41 82

The relative sensitivity of urinary enzyme measurements for detecting renal damage was determined for two nephrotoxins. Injection of a single dose of sodium phosphate (10 mmoles/kg) caused damage to the proximal tubules and led to a 15 fold increase in lactate dehydrogenase (LDH) activity excreted into the urine. In contrast to this change the serum LDH remained normal. Similar results were obtained following the injection of cephaloridine (2 g/kg) with an 18 fold increase in urinary LDH and a marginal increase in urinary glutamate dehydrogenase (GDH). By contrast the serum LDH was unchanged. Urinary enzymes are therefore more sensitive for detecting renal injury than enzymes. The four enzymes investigated are located in specific regions of the cell so that the involvement of the organelles and regions of the cell can be followed. Damage to the organelles does not appear to occur as the excretion of the lysosomal enzymes remained normal and only in the case of cephaloridine were marginal changes in the mitochondrial GDH excretion seen. The average alkaline phosphatase was also normal suggesting no gross damage to the plasma membrane although a few individual rats excreted abnormal activities of alkaline phosphatase. These rats however, also excreted high activities of LDH. This suggests that damage to the membrane causes leakage of LDH and in severe cases release of the plasma membrane enzyme alkaline phosphatase. The administration of cephaloridine at various doses showed that urinary enzyme measurements were as sensitive as histology for demonstrating renal damage and that of these enzymes, LDH was by far the most useful.
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PMID:The sensitivity of urinary enzyme measurements for detecting renal injury. 44 87

Cross-linking of the unimer of glutamate dehydrogenase from beef liver (consisting of six polypeptide chains each having a molecular weight of 56000) with dimethyladipimidate and subsequent analysis by sodium dodecylsulfate electrophoresis shows predominantly the trimeric species (molecular weight 168000). Treatment with dimethylimidates of other chain length yields significantly less trimeric species indicating that the amino groups being cross-linked are within a distance of about 0.85 nm. Comparison of the molar amount of incorporated [14C]dimethyladipimidate with the number of modified amino groups (determined with trinitrobenzenesulfonic acid) shows that although 8-9 of the 34 amino groups have reacted, only 2-3 of them are involved in cross-links. Reaction with dimethylimidates inactivates the enzyme. The loss of the activity is partly concomitant to cross-linking to the trimeric species and not simply due to the modification of essential lysine residues. This is supported by the fact that, although more lysine residues react with mono-functional methylimidates, the loss of activity is reduced. Purified chymotryptic and tryptic peptides of the radioactive-labeled trimeric species were subjected to sequence analysis. Six peptides containing 75% of the total label were identified: one involves the amino-terminal residue alanine-1 and the others involve lysine-105, lysine-154, lysine-269, lysine-358 and lysine-399. Quantitative analysis of the specific radioactivity of each peptide/mol lysine leads to the conclusion that only lysine-105, lysine-154, lysine-269 and lysine-358 participate in cross-links, lysine-269 and lysine-358, respectively, being at isologous and lysine-105 cross-linked with lysine-154 at heterologous contact domains of the enzyme. A model for the planar arrangement of the trimeric species in the quaternary structure of glutamate dehydrogenase is discussed. It includes both isologous and heterologous contact areas between the polypeptide chains.
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PMID:Studies of glutamate dehydrogenase. Analysis of quaternary structure and contact areas between the polypeptide chains. 55 96

Rats were subjected for 2 weeks to separate and combined exposures to mercuric chloride and sodium selenite at doses of 0.5 mg Hg/kg and 0.5 mg Se/kg. The content of mercury, selenium and protein as well as the activities of glutamate dehydrogenase (GLDH) and malate dehydrogenase (MDH) were determined in homogenates, mitochondria and intramitochondrial structures of the exposed animals. It was found that both separate and combined exposures of rats to mercuric chloride and sodium selenite inhibited GLDH activity and did not affect MDH activity in the examined organs. Mercury-selenium interaction brought about a decrease in the content of mercury in the intramitochondrial structures of kidneys and an increased accumulation of both elements in the outer and inner membranes of liver mitochondria. The biochemical mechanism of mercury-selenium interaction is discussed.
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PMID:Activity of glutamate and malate dehydrogenases in liver and kidneys of rats subjected to multiple exposures of mercuric chloride and sodium selenite. 64 59

Dicarboxylic amino acids constitute the most numerous residues of insoluble elastin in which are potentially ionizable in the physiological range of pH. These residues are essential in facilitating productive electrostatic interaction between elastase and elastin. The present study has investigated the possibility that the glutamic and aspartic acid residues of elastin are amidated. Acid-labile amide-bound ammonia of elastin was quantitated after hydrolysis of the insoluble protein with 2 M HC1 by incubating aliquots of microdistilled hydrolysates with glutamate dehydrogenase, excess alpha-ketoglutarate, and reduced nicotinamide adenine dinucleotide and measuring the resultant decrease in A340 due to oxidation of the dinucleotide cofactor. It was found that ligament elastin purified by repeated autoclaving contains approximately 2.29 mumol of acid-labile amide nitrogen per 10 mg of protein, a value equivalent to approximately 70% of the total number of dicarboxylic amino acid residues. Independent analysis of the amide content was obtained by amino acid analysis of an esterified and reduced elastin sample in which the free dicarboxylic amino acid residues had been converted to the corresponding alcohol derivatives. This analysis indicated that autoclaved ligament elastin contains approximately 18 glutamine, 3 asparagine, 4 glutamic acid and 5 aspartic acid residues per 1000 residues, in good agreement with the analysis of total acid-labile ammonia. The esterified and reduced elastin derivative was nearly inert as an elastase substrate, consistent with a lack of free dicarboxylic amino acid residues. However, addition of sodium dodecyl sulfate to this elastin derivative restores enzyme-substrate charge complementarity, and the elastin-ligand complex was readily hydrolyzed by elastase at the fully stimulated rate, emphasizing the control such ligands can exert in elastolysis. The amide bonds of elastin were found to be significantly more resistant to hydrolysis by 0.1 M NaOH at 98 degrees C than were those of lysozyme or free amidated amino acids. The finding that most of dicarboxylic amino acid residues of elastin exist at neutral amides further emphasizes the apolar character of elastin and has bearing upon the metabolic susceptibility, ligand-binding ability and structural aspects of this connective tissue protein.
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PMID:Amidated carboxyl groups in elastin. 93 66

In extension of a previous study with yeast glucose-6-P dehydrogenase (Kawaguchi, A., and Bloch, K. (1974) J. Biol. Chem. 249, 5793-5800), the structural changes accompanying the inhibition of glutamate dehydrogenase and several malate dehydrogenases by palmitoyl-CoA and by sodium dodecyl sulfate have been investigated. Palmitoyl-CoA converts liver glutamate dehydrogenase to enzymatically inactive dimeric subunits (Mr = 1.2 X 10(5)) and tightly binds to the dissociated enzyme. Removal of the inhibitor from the palmitoyl-CoA-dimer complex fails to regenerate enzyme activity. The Ki values for palmitoyl-CoA inhibition of malate dehydrogenases (oxalacetate reduction) are, for the enzyme from pig heart mitochondria, 1.8 muM, 500 muM from pig heart supernatant, and 10 muM from chicken heart supernatant. These inhibitions are readily reversible. Palmitoyl-CoA does not alter the quaternary structure of any of the malate dehydrogenases and binds only weakly to these enzymes. Mitochondrial malate dehydrogenase assayed in the direction malate to oxalacetate is much less sensitive to palmitoyl-CoA, with Ki values of 50 muM at pH 10 and greater than 50 muM at pH 7.4. While the differences in palmitoyl-CoA sensitivity in the forward and backward reactions catalyzed by mitochondrial dehydrogenase are unexplained, a physiological rationale for these differential effects is offered. Sodium dodecyl sulfate dissociates the various dehydrogenases to monomeric subunits in contrast to the more selective effects of palmitoyl-CoA.
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PMID:Inhibition of glutamate dehydrogenase and malate dehydrogenases by palmitoyl coenzyme A. 125 73

The isoenzymatic pattern of glutamate dehydrogenase (GDH) has been described for Ascaris suum a parasite of Sus scrofa domestica. Only one band of activity has been revealed, suggesting a monomorphic condition for this enzyme. Also, the structure of GDH has been assayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining. Only one subunit was present with a molecular weight of about 55,000. A hexameric structure for GDH of A. suum is suggested.
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PMID:Isoenzymatic pattern and structure of glutamate dehydrogenase from Ascaris suum. 129 99


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