Activity of several enzymes of amino acid catabolism in the liver of rats fed protein as a meal

Bourdel, G; Hitier, Y; Lardeux, Bernard; Girard-Globa, Anik; Forestier, Marguerite; Gouhot, Betty; Khol, Claude

doi:10.1051/rnd:19830607

Cited by 2 publications

(2 citation statements)

References 15 publications

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“…As for the down-regulated genes, the decrease of fatty acid synthase and stearoyl CoA desaturase, both are in the pathway of fatty acid synthesis, which might reflect a decrease in the need of fatty acid. Serine dehydratase and ornithine aminotransferase are known to be induced by high protein diet, glucagon, or glucocorticoid (Hunter and Harper, 1977;Bourdel et al, 1983). Based on the present data, it is difficult to conclude whether the change was due to the relative reduction of protein in the diet, or to the secondary change in endocrinological status.…”

Section: Discussionmentioning

confidence: 47%

Effect of the difference in vehicles on gene expression in the rat liver—analysis of the control data in the Toxicogenomics Project Database

et al. 2006

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Section: Discussionmentioning

confidence: 47%

Effect of the difference in vehicles on gene expression in the rat liver—analysis of the control data in the Toxicogenomics Project Database

et al. 2006

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“…Besides age-related variations ( 17 , 20 , 21 ) , protein supply is also a key regulator of hepatic and intestinal (but not renal) OAT activity ( 22 , 23 ) . A protein load is followed by a rapid and marked induction of hepatic OAT, with normalisation in nearly 12 h ( 23 ) .…”

mentioning

confidence: 99%

Overexpression of ornithine aminotransferase: consequences on amino acid homeostasis

et al. 2008

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Ornithine aminotransferase (OAT) is a reversible enzyme expressed mainly in the liver, kidney and intestine. OAT controls the interconversion of ornithine into glutamate semi-aldehyde, and is therefore involved in the metabolism of arginine and glutamine which play a major role in N homeostasis. We hypothesised that OAT could be a limiting step in glutamine -arginine interconversion. To study the contribution of the OAT enzyme in amino acid metabolism, transgenic mice that specifically overexpress human OAT in the liver, kidneys and intestine were generated. The transgene expression was analysed by in situ hybridisation and real-time PCR. Tissue (liver, jejunum and kidney) OAT activity, and plasma and tissue (liver and jejunum) amino acid concentrations were measured. Transgenic male mice exhibited higher OAT activity in the liver (25 (SEM 4) v. 11 (SEM 1) nmol/min per mg protein for wild-type (WT) mice; P, 0·05) but there were no differences in kinetic parameters (i.e. K m and maximum rate of reaction (V max )) between WT and transgenic animals. OAT overexpression decreased plasma and liver ornithine concentrations but did not affect glutamine or arginine homeostasis. There was an inverse relationship between ornithine levels and OAT activity. We conclude that OAT overexpression has only limited metabolic effects, probably due to the reversible nature of the enzyme. Moreover, these metabolic modifications had no effect on phenotype. Ornithine: Arginine: GlutamineOrnithine aminotransferase (OAT; L-ornithine 2-oxo acid aminotransferase; EC 2.6.1.13) is a pyridoxal-5 0 -phosphate-dependent mitochondrial matrix aminotransferase that catalyses the interconversion of ornithine into glutamate semi-aldehyde, which is in spontaneous equilibrium with its cyclic tautomer, pyrroline-5-carboxylate (P5C). In contrast to other aminotransferases, this reaction enables the reversible transfer of the ornithine v-amino group. It depends on two tyrosine residues leading to the interaction with ornithine and the protection of the v-amino group against hydrolysis (1) .OAT is localised at a crossing between two important metabolisms, with arginine and polyamine metabolism on one side and glutamate and proline metabolism on the other (Fig. 1).Although OAT is expressed constitutively in many tissues, it is mainly found in the liver, kidney (at higher levels in females) and the small intestine (2,3) where its response to hormones and variations in dietary protein intake is subject to complex regulation mechanisms (2,4,5) . The reaction is directed towards glutamate semi-aldehyde synthesis in the liver and kidneys and towards ornithine synthesis in the small intestine. Hepatic OAT expression is restricted to perivenous hepatocytes (4) and co-localised with glutamine synthetase expression (6) , which suggests that OAT plays a major role in N homeostasis. In the kidney, Levillain et al. (7) showed that OAT is distributed along the whole nephron, but its activity is higher in proximal tubules than in distal tubules. In the intestine, OAT is...

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Activity of several enzymes of amino acid catabolism in the liver of rats fed protein as a meal

Abstract: Summary. Rats

Cited by 2 publications

References 15 publications

Effect of the difference in vehicles on gene expression in the rat liver—analysis of the control data in the Toxicogenomics Project Database

Effect of the difference in vehicles on gene expression in the rat liver—analysis of the control data in the Toxicogenomics Project Database

Overexpression of ornithine aminotransferase: consequences on amino acid homeostasis

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