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)

Enzyme activities and DNA content have been measure in axolotl liver during the metamorphic period (4-8 months after spawning). Three different types of enzyme activity profiles were observed. In the type I profile (carbamoyl-phosphate synthase, arginase, ornithine transcarbamoylase, and glutamate dehydrogenase) enzyme activity is high in the youngest animals studied, and shows a minimum at 5 months followed by a maximum at 8 months of age. Thereafter activities do not change or slightly decrease. In the type II profile (tyrosine aminotransferase, glucose-6-phosphatase) enzyme activity shows a peak at 5 months of age and is low thereafter. Hexokinase, the enzyme with a type III profile, shows high activity throughout the metamorphic period. DNA content remains high throughout the metamorphic period but decreases 50% between 9 and 12 months of age, probably due to an increase in the size of the hepatocytes. No glucokinase activity was detected. High activities of cluster II enzymes represent early metamorphic events, while the rising part of cluster I is associated with late metamorphic events. The apparent molecular specific activity increases during natural development between 5 and 9 months of age, or precociously, upon thyroid hormone treatment. This change in apparent molecular specific activity is correlated to the advent of ureotelism.
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PMID:Enzyme clusters during the metamorphic period of Ambystoma mexicanum: role of thyroid hormone. 612 71

Serum glutamate dehydrogenase (GDH) activity was greatly raised (up to 830 times the upper limit of normal) in 16 patients with Reye's syndrome. The serum activity was masked by an inhibitor, and the rises were observed only after dialysis or sample dilution. Serum GDH values from 38 paediatric patients, including 10 with hyperammonaemia due to other causes, showed no such rise after dialysis. Only 1 of 13 adult patients with liver disease had high GDH activity, but this level was not increased after dialysis. Serum ornithine carbamyl transferase activity was also raised in patients with Reye's syndrome, but levels were not increased after dialysis. The ratio of dialysed/undialysed GDH activity clearly distinguished all Reye's patients from controls. The inhibition of a mitochondrial enzyme which regulates ammonia metabolism may contribute to the hyperammonaemia of Reye's syndrome. Serum GDH levels before and after dialysis would seem to be a useful diagnostic aid in Reye's disease.
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PMID:Masking by enzyme inhibitor of raised serum glutamate dehydrogenase activity in Reye's syndrome. 613 99

Lactate (LDH) and succinate (SDH) dehydrogenases activities decreased in red and white muscles of rat under acute ethanol loading indicating the inhibition of energy metabolism and stepped up lactic acid formation under stress conditions. Aspartate aminotransferase (AAT) and glutamate dehydrogenase (GDH) were found to increase. In contrast to these, the AMP deaminase activity decreased in white muscle suggestive of decreased deamination of nucleic acids. The ornithine cycle enzymes such as argininosuccinate synthetase (ArSS) and arginase indicated diminished activities showing low level of operation of urea cycle and consequent accumulation of ammonia was observed in red muscle with low production of glutamine, whereas in the case of white muscle this trend is reversed. The possible alterations of ethanol toxicity on energy requirements, transdeamination patterns, ureogenesis and glutamine production have been discussed.
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PMID:Metabolic alterations in the red and white muscles of rat to acute ethanol treatment. 618 32

Differential digitonin extraction of rat liver mitochondria and of mitochondria of livers of affected and unaffected male sparse fur mice released a lysine transcarbamylase activity from the mitochondria at a digitonin to protein ratio in between that for myokinase and glutamate dehydrogenase, but at a slightly lower ratio than the ornithine transcarbamylase activity. Homocitrulline formation by isolated rat liver mitochondria is independent of the uptake of lysine by mitochondria as evidenced by the insensitivity of homocitrulline formation to changes in the matrix pH, in contrast to citrulline formation from ornithine. High-performance liquid chromatography separates the lysine transcarbamylase activity from the ornithine transcarbamylase activity. It is concluded that the lysine transcarbamylase activity is localized outside the inner mitochondrial membrane.
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PMID:Further evidence for a separate enzymic entity for the synthesis of homocitrulline, distinct from the regular ornithine transcarbamylase. 643 2

The role of glucocorticosteroid and thyroid hormone and of glucagon and insulin in the pre- and postnatal developmental formation of carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, glutamate dehydrogenase, tyrosine aminotransferase, glucose-6-phosphatase, hexokinase and glucokinase activities in rat liver was investigated. Glucocorticosteroids and a low insulin/glucagon ratio always stimulate formation of carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, glutamate dehydrogenase, tyrosine aminotransferase and glucose-6-phosphatase, while glucocorticosteroids and a high insulin/glucagon ratio stimulate formation of glucokinase. Thyroid hormone stimulates the formation of carbamoyl-phosphate synthase, arginase and tyrosine aminotransferase only before birth, whereas it stimulates the formation of glutamate dehydrogenase and glucose-6-phosphatase both before and after birth. Ornithine transcarbamoylase activity is depressed after thyroid-hormone treatment before and after birth. DNA content is always decreased by glucocorticosteroids and increased by thyroid hormone. The effect of these hormones on hexokinase is complex, probably due to different responses of the constitutive isozymes. With the exception of the effects of thyroid hormone on carbamoyl-phosphate synthase, arginase and tyrosine aminotransferase before birth, which may be indirect, the responses of enzyme activities and DNA content to treatment with glucocorticosteroid hormones, glucagon, insulin and thyroid hormone are qualitatively the same in fetuses, neonates, sucklings, weanlings and adults. Thus, the developmental profiles of the enzyme clusters reflect the changing levels of the relevant hormones. The enzymes that are stimulated by glucocorticosteroids and the insulin/glucagon ratio show increases in enzyme activity perinatally and around weaning, and relatively low activities in between, while those enzymes that are additionally stimulated by thyroid hormone differ in exhibiting relatively high activities between birth and weaning.
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PMID:Multihormonal control of enzyme clusters in rat liver ontogenesis. II. Role of glucocorticosteroid and thyroid hormone and of glucagon and insulin. 702 60

Ornithine metabolism is coupled to oxidative phosphorylation in isolated rat liver mitochondria. The pathway involving ornithine: alpha-ketoglutarate transaminase (OKT), glutamic semialdehyde dehydrogenase (GSDH), and glutamate dehydrogenase (GDH) with cycling of alpha-ketoglutarate-glutamate at the OKT reaction appears to be involved. Ornithine may be utilized by this pathway to sustain ATP levels during mitochondrial energy-deficiency states with resultant decreased urea-cycle flux and increased ammonia production. This pathophysiologic mechanism suggests that hyperammonemia is a consequence of an energy-deficiency state. Therapy directed toward alleviating the energy-deficiency state may be more beneficial than efforts to reduce ammonia levels.
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PMID:Urea cycle regulation: I. Coupling of ornithine metabolism to mitochondrial oxidative phosphorylation. 718 96

The role of glucocorticosteroid hormones in the developmental formation of carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, glutamate dehydrogenase, tyrosine aminotransferase, glucose-6-phosphatase, hexokinase and glucokinase activities in rat liver was investigated. Steroid hormone producing glands were either inactivated by hypophysectomy (before birth) or removed by adrenalectomy and/or gonadectomy (after birth). These procedures strongly depressed corticosterone levels. Furthermore, they decreased enzyme activities when performed before birth or after the second postnatal week. However, adrenalectomy at 1 week of age was less effective: the developmental increases in carbamoyl-phosphate synthase, ornithine transcarbamoylase, arginase, tyrosine aminotransferase and glucose-6-phosphatase activity persisted despite the absence of increasing levels of circulating corticosterone.
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PMID:Multihormonal control of enzyme clusters in rat liver ontogenesis. I. Effects of adrenalectomy and gonadectomy. 727 92

Mitochondria isolated from systemic hearts of the squid Illex illecebrosus showed high respiratory control ratios, and, with appropriate substrates, the expected ADP/O ratios. Of amino acids tested, proline and ornithine were oxidized at highest rates; of carboxylates, malate, succinate and pyruvate gave the highest state-3 respiration rates. Pyruvate oxidation is enhanced with proline, ornithine, and 1-pyrroline-5-carboxylate (pyrroline carboxylate) all of which can serve to augment the Krebs cycle. However, proline, ornithine and pyrroline carboxylate oxidation is not similarly dependent upon pyruvate. Rotenone inhibited state-3 respiration of malate, proline, ornithine and pyrroline carboxylate. Neither intermediates of fatty acid oxidation nor glycerol 3-phosphate were utilized at significant rates. Key enzymes in proline and ornithine oxidation, i.e. proline dehydrogenase, pyrroline-carboxylate dehydrogenase, ornithine aminotransferase, and glutamate dehydrogenase were located in the mitochondria. The synthesis of proline is catalyzed by pyrroline-carboxylate reductase, which was found exclusively in the cytosol. The respiration, phosphorylation and enzyme data taken together suggest that the main carbon sources for heart mitochondria of Illex are pyruvate plus the proline and ornithine pool.
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PMID:Respiratory and enzymatic properties of squid heart mitochondria. 731 31

1. Protein-free extracts of isolated rat-liver mitochondria contain 5.17 +/- 0.19 nmol ammonia/mg protein [cf. Harris, E. J. and Bassett, D. J. (1971) FEBS Lett. 19, 214-217]. 2. The ammonia found in the protein-free extracts does not originate from lysosomes contaminating the mitochondrial preparation. 3. When isolated mitochondria are incubated with ornithine, 14CO2 and a source of ATP a small amount of citrulline is formed. This amount is stoichiometrically equivalent to the ammonia that disappears from the extramitochondrial space, whereas the amount of ammonia found in the protein-free extracts of the mitochondria remains unchanged. Similar results were obtained when the reductive amination of 2-oxoglutarate was used as an ammonia-consuming reaction. 4. When isolated mitochondria are incubated under conditions such that the glutamate dehydrogenase and 3-hydroxybutyrate dehydrogenase reactions reach equilibrium, the thermodynamically active concentration of ammonia is not equal to the concentration measured in the protein-free extracts. 5. About 80% of the ammonia found in protein-free extracts of rat-liver mitochondria is derived from a component or components with a molecular weight of greater than or equal to 50,000. 6. Protein-free extracts of isolated rat-liver cells contain considerable amounts of ammonia. After digitonin fractionation this ammonia is found in the protein-free extract of the particulate fraction. 7. It is concluded that the ammonia found in protein-free extracts of rat-liver tissue is derived from a component or components in the mitochondria and is released during deproteinization.
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PMID:Origin of the ammonia found in protein-free extracts of rat-liver mitochondria and rat hepatocytes. 743 58

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.
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PMID:[3H]-amino acid uptake and metabolic studies on Gigantocotyle explanatum and Gastrothylax crumenifer (Digenea: Paramphistomidae). 763 32


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