Cysteine sulfinate transamination activity of aspartate aminotransferases

Abstract

Aspartate aminotransferases from pig heart cytosol and mitochondria, Escherichia coli B and Pseudomonas striata accepted L-cysteine sulfinate as a good substrate. The mitochondrial isoenzyme and the Escherichia enzyme showed higher activity toward L-cysteine sulfinate than toward the natural substrates, L-glutamate and L-aspartate. The cytosolic isoenzyme catalyzed the L-cysteine sulfinate transamination at 50% the rate of L-glutamate transamination. The Pseudomonas enzyme had the same reactivity toward the three substrates. Antisera against the two isoenzymes and the Escherichia enzyme inactivated almost completely cysteine sulfinate transamination activity in the crude extracts of pig heart muscle and Escherichia coli B, respectively. These results indicate that cysteine sulfinate transamination is catalyzed by aspartate aminotransferase in these cells.