The Metabolism of Mitochondrial Proteins

In 1963, the existence of two isozymes of alanine aminotransferase (Galanine : 2-oxoglutarate aminotransferase, EC 2.6.1.2) was still somewhat in doubt.Hird and Rowsell (2) reported that alanine aminotransferase was present in the particulate fraction as well as in the soluble phase of rat liver homogenates, and they speculated that the activity was of mitochondrial origin.However, in studies of the release of aminotransferases into serum following liver injury, Fleisher and Wakim (3), using electrophoresis, found only a single alanine aminotransferase, although they discerned both isozymes of aspartate aminotransferase.Segal, Beattie, and Hopper (4), in an extensive study of hepatic alanine aminotransferase, detected only a soluble form of the enzyme.Nevertheless, reports of the existence of a mitochondrial enzyme continue to be published.Kafer and Pollak (5) found 20% of the total alanine aminotransferase activity of liver homogenates in the mitochondrial fraction, and Katunuma