Characteristics of hepatic alanine-glyoxylate aminotransferase in different mammalian species.
Mitochondrial extracts of dog, cat, rat and mouse liver contain two forms of alanine-glyoxylate aminotransferase (EC 2.6.1.44): one, designated isoenzyme 1, has mol.wt. approx. 80 000 and predominates in dog and cat liver; the other, designated isoenzyme 2, has mol.wt. approx. 175 000 and predominates in rat and mouse liver. In rat and mouse liver, isoenzyme 1 activity was increased by the injection in vivo of glucagon, but not isoenzyme 2 activity. Isoenzyme 1 was purified and characterized from liver mitochondrial extracts of the four species. Both rat and mouse enzyme preparations catalysed transamination between a number of L-amino acids and glyoxylate, and with L-alanine as amino donor the effective amino acceptors were glyoxylate, phenylpyruvate and hydroxypyruvate. In contrast, both dog and cat enzyme preparations were specific for L-alanine and L-serine with glyoxylate, and used glyoxylate and hydroxypyruvate as effective amino acceptors with L-alanine. Evidence that isoenzyme 1 is identical with serine-pyruvate aminotransferase (EC 2.6.1.51) was obtained. Isoenzyme 2 was partially purified from mitochondrial extracts of rat and mouse liver. Both enzyme preparations were specific for L-alanine and glyoxylate. On the basis of physical properties and substrate specificity, it was concluded that isoenzyme 2 is a separate enzyme. Some other properties of isoenzymes 1 and 2 are described.
D000410:Alanine Transaminase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002415:Cats; D004285:Dogs; D006038:Glyoxylates / Q000378:metabolism; D007527:Isoenzymes / Q000302:isolation & purification; D007538:Isoniazid / Q000494:pharmacology; D051379:Mice; D008930:Mitochondria, Liver / Q000201:enzymology*; D011773:Pyruvates / Q000378:metabolism; D051381:Rats; D012663:Semicarbazides / Q000494:pharmacology; D013379:Substrate Specificity
D000596:Amino Acids; D006038:Glyoxylates; D007527:Isoenzymes; D011773:Pyruvates; D012663:Semicarbazides; D000410:Alanine Transaminase; D007538:Isoniazid