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 activities of 12 enzymes, many related to ornithine metabolism, were measured in rat submaxillary gland, submaxillary gland tumors and pancreas. In submaxillary gland, the activities of arginase, ornithine aminotransferase, pyrroline-5-carboxylate reductase and glutamine synthetase were high, but no ornithine transcarbamylase or proline oxidase could be detected. In the fetal submaxillary gland, arginase was at almost adult levels while ornithine aminotransferase reached 50% of its adult value postnatally. Submaxillary tumors deviated from their cognate tissue by lower levels of amino acid metabolizing enzymes and by high concentrations of thymidine kinase. In pancreas, none of the pyrroline-5-carboxylate metabolizing enzymes were as high as in either liver or submaxillary gland. The outstanding activities were those of gamma-glutamyl transpeptidase and glutamate dehydrogenase. Although arginase activities in submaxillary gland and pancreas were quantitatively similar, they differed qualitatively: submaxillary gland contained the same variant as liver while the pancreatic isozymes resembled those of other nonhepatic tissues.
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PMID:Amino acid metabolizing enzymes in rat submaxillary gland, normal or neoplastic, and in pancreas. 0 9

In previous studies it was found that: (a) aspartate aminotransferase increases the aspartate dehydrogenase activity of glutamate dehydrogenase; (b) the pyridoxamine-P form of this aminotransferase can form an enzyme-enzyme complex with glutamate dehydrogenase; and (c) the pyridoxamine-P form can be dehydrogenated to the pyridoxal-P form by glutamate dehydrogenase. It was therefore concluded (Fahien, L.A., and Smith, S.E. (1974) J. Biol. Chem 249, 2696-2703) that in the aspartate dehydrogenase reaction, aspartate converts the aminotransferase into the pyridoxamine-P form which is then dehydrogenated by glutamate dehydrogenase. The present results support this mechanism and essentially exclude the possibility that aspartate actually reacts with glutamate dehydrogenase and the aminotransferase is an allosteric activator. Indeed, it was found that aspartate is actually an activator of the reaction between glutamate dehydrogenase and the pyridoxamine-P form of the aminotransferase. Aspartate also markedly activated the alanine dehydrogenase reaction catalyzed by glutamate dehydrogenase plus alanine aminotransferase and the ornithine dehydrogenase reaction catalyzed by ornithine aminotransferase plus glutamate dehydrogenase. In these latter two reactions, there is no significant conversion of aspartate to oxalecetate and other compounds tested (including oxalacetate) would not substitute for aspartate. Thus aspartate is apparently bound to glutamate dehydrogenase and this increases the reactivity of this enzyme with the pyridoxamine-P form of aminotransferases. This could be of physiological importance because aspartate enables the aspartate and ornithine dehydrogenase reactions to be catalyzed almost as rapidly by complexes between glutamate dehydrogenase and the appropriate mitochondrial aminotransferase in the absence of alpha-ketoglutarate as they are in the presence of this substrate. Furthermore, in the presence of aspartate, alpha-ketoglutarate can have little or no affect on these reactions. Consequently, in the mitochondria of some organs these reactions could be catalyzed exclusively by enzyme-enzyme complexes even in the presence of alpha-ketoglutarate. Rat liver glutamate dehydrogenase is essentially as active as thebovine liver enzyme with aminotransferases. Since the rat liver enzyme does not polymerize, this unambiguously demonstrates that monomeric forms of glutamate dehydrogenase can react with aminotransferases.
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PMID:Effect of aspartate on complexes between glutamate dehydrogenase and various aminotransferases. 1 47

1) A lysosomal protease, a new cathepsin that inactivates glucose-6-phosphate dehydrogenase [EC 1.1.1.49] and some other enzymes and differs from cathepsin B [EC 3.4.22.1] was purified about 2,200-fold from crude extracts of rat liver by cell-fractionation, freezing and thawing, acetone treatment, gel filtration, and DEAE Sephadex and CM-Sephadex column chromatographies. 2) The new cathepsin was markedly activated by the thiol-reagent, 2-mercaptoethanol and inhibited by monoiodoacetate. 3) The molecular weight of the new cathepsin was found by Sephadex G-75 column chromatography to be 22,000, which is smaller than that of cathepsin B. 4) The optimum pH of the enzyme for inactivation of glucose-6-phosphate dehydrogenase was pH 5.0--5.5. The enzyme was unstable in alkali and on heat treatment. 5) The rates of inactivation of glucose-6-phosphate dehydrogenase, apo-ornithine aminotransferase [EC 2.6.1.13], apo-tyrosine aminotransferase [EC 2.6.1.5], apo-cystathionase [EC 4.4.1.1], glucokinase [EC 2.7.1.2], glyceraldehyde-3-phosphate dehydrogenase [EC 1.2.1.12], and malate dehydrogenase [EC 1.1.1.37] by the new cathepsin were higher than those by cathepsin B. However aldolase [EC 4.1.2.13] was inactivated more rapidly by cathepsin B than by the new cathepsin. Lactate dehydrogenase [EC 1.1.1.27], glutamate dehydrogenase [EC 1.4.1.2] and alcohol dehydrogenase [EC 1.1.1.1] were not inactivated by either cathepsin. Unlike cathepsin B, the new cathepsin scarcely hydrolyzes N-substituted derivatives of arginine.
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PMID:Purification and properties of a new cathepsin from rat liver. 3 59

A chromatographic-videodensitometric assay was found to be appropriate for measuring the activity of glutamate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, ornithine-2-oxoacid aminotransferase and histidine ammonia-lyase in human tissue homogenates. From the assay mixtures containing substrate(s), cofactor(s), buffer and tissue extract, five or ten microliters samples were taken at different time intervals and chromatographed on Dowex 50 X 8 type resin-coated chromatosheets. On each chromatoplate 50 nmoles of the amino acid to be measured were separately run as a reference for videodensitometric evaluation. By comparing the density of the reference amino acid to that of the individual samples the molar amount of amino acids formed or consumed in the reaction could be calculated. The present findings suggest that the chromatographic-videodensitometric microassay (CV-technique) is suitable for measuring the activity of amino acid transforming enzymes in minute amounts of tissue extracts.
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PMID:Determination of enzyme activity by chromatography and videodensitometry. I. Microassay of amino acid transforming enzymes in human tissue homogenates. 54 67

The direction and capacity for the metabolism of delta1-pyrroline-5-carboxylate in a number of rat tissues ere investigated by measuring the activities of delta1-pyrroline-5-carboxylate reductase, delta1-pyrroline-5-carboxylate dehydrogenase and proline oxidase. Each of these enzymes catalyzed unidirectional reactions in which delta1-pyrroline-5-carboxylate was either the substrate or product. Delta1-Pyrroline-5-carboxylate reductase activities that were much higher than any previously reported were obtained by avoiding its inactivation in the cold. delta1-Pyrroline-5-carboxylate dehydrogenase, previously said to act on both D- and L-isomers of delta1-pyrroline-5-carboxylate, acted only on the L-isomer. Proline oxidase could not be measured in two adult tissues, in which an inhibitor appeared after birth. The activity of delta1-pyrroline-5-carboxylate reductase significantly paralleled that of ornithine aminotransferase in 23 tissues, showing a widespread potential for proline synthesis from ornithine. An independently distributed potential in fewer tissues for proline degradation to alpha-oxoglutarate was shown by the significantly similar tissue distributions of proline oxidase. Delta1-pyrroline-5-carboxylate dehydrogenase and glutamate dehydrogenase. Reverse metabolism of glutamate or proline to ornithine would be atypical in rat tissues with these distributions of unidirectional enzyme reactions.
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PMID:Enzymes metabolizing delta1-pyrroline-5-carboxylate in rat tissues. 90 23

Urea cycle enzymes are all shown to be active in dolphin liver. Acetylglutamate-independent cytoplasmic carbamylphosphate synthase is also present. Arginase is a basic protein, although less markedly basic than the dog enzyme. It is 118 per cent activated by heating at 50 degrees. Optimum pH is 10.5. Co++ and Ni++ inhibit the enzyme. AMP deaminase, glutamicoxaloacetic transaminase, glutamate dehydrogenase and ornithine transaminase are also active in dolphin liver.
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PMID:Urea cycle enzymes in the liver of a dolphin Platanista indi. 95 55

A new spectrophotometric procedure is described for determining glutamate-dependent activities of aspartate aminotransferase, alanine aminotransferase, and ornithine aminotransferase with NADPH-linked glutamate dehydrogenase (GDH) from nitrate-grown Stichococcus bacillaris. The algal NADPH-GDH is highly specific for oxoglutarate and can catalyze the reduction of this keto acid in the presence of high glutamate concentrations, and thus is suitable for the measurement of oxoglutarate produced in glutamate-dependent amino-transferase reactions. The alga produces large amounts of NADPH-GDH which can be adequately purified in a few simple steps. The purified enzyme can be stored at 4 degrees C for several weeks without any detectable loss of activity. The algal NADPH-GDH can also be used for the estimation of small amounts of oxoglutarate in aqueous extracts.
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PMID:A spectrophotometric procedure for measuring oxoglutarate and determining aminotransferase activities using nicotinamide adenine dinucleotide phosphate-linked glutamate dehydrogenase from algae. 255 50

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.
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PMID:A glutamate dehydrogenase-based method for the assay of L-glutamic acid: formation of pyridine nucleotide fluorescent derivatives. 257 90

Livers of rats between the 16th gestational and 100th postnatal day of age were subjected to quantitative biochemical and electron microscope, morphometric analyses. The amount of total mitochondrial protein per gram of liver remained at 34% of the adult level throughout the last 4 days of gestation but this was the period of rapid rise in the levels of cytochrome c oxidase, aspartate aminotransferase, and glutamate dehydrogenase in mitochondria; the nuclear fraction also acquired some glutamate dehydrogenase but lost most of it during postnatal development. During early postnatal life the amount of mitochondrial protein rose in parallel with the levels of cytochrome c oxidase and glutamate dehydrogenase but the upsurges of glutaminase and, later, of ornithine aminotransferase were accompanied by relatively little change in total mitochondrial protein. The surface area of rough endoplasmic reticulum per unit volume of hepatocyte cytoplasm (S(v) (RER)) did not change significantly throughout the period of development studied. From the 16th day of gestation to term the surface area of smooth ER (S(v) (SER)), the volume occupied by mitochondria (V(v) (MT)) and their number (N(v) (MT)) remained at 30, 66, and 45% of their adult values, respectively. V(v) (MT) and N(v) (MT) attained their maximal levels by the 2nd postnatal day and S(v) (SER) between days 2 and 12. Mitochondria of adult liver are thus smaller and contain more protein per unit volume than do those of fetal liver. After the 12th postnatal day, hepatocytes treble their size; they acquire more cytoplasm with additional enzymes but without further change in organelle concentration. The data reveal several distinct phases in the differentiation of hepatocytes. Each phase can be characterized by the extent to which the quantity and composition of various subcellular compartments evolve.
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PMID:Subcellular morphometric and biochemical analysis of developing rat hepatocytes. 434 89

1. Homogenates of liver or kidney from rat, mouse, dog and guinea pig formed ornithine from proline but not from glutamate. Rat kidney was most active in this reaction and was used for further studies. 2. The overall reaction was found to be catalysed by proline oxidase to yield glutamic gamma-semialdehyde, followed by transamination of this product with glutamate as catalysed by ornithine-keto acid aminotransferase. 3. The unfavourable equilibrium of the ornithine-keto acid aminotransferase reaction was overcome chiefly by glutamate dehydrogenase in the tissue, which removed the alpha-oxoglutarate produced, by reduction with endogenous ammonia and NADH. 4. Aspartate aminotransferase in these preparations also aided in the removal of alpha-oxoglutarate. In this case the overall reaction was driven also by the rapid decarboxylation of oxaloacetate. 5. No evidence could be found for a pathway of ornithine synthesis involving acylated intermediates as has been observed in some micro-organisms. 6. The rate of ornithine synthesis in homogenates of several rat tissues paralleled the activity of ornithine-keto acid aminotransferase in these tissues, indicating that this enzyme was rate-determining for the synthesis. 7. The possible influence of these reactions on urea synthesis is discussed.
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PMID:The formation of ornithine from proline in animal tissues. 604 97


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