Purification and characterization of mitochondrial cysteine aminotransferase from rat liver.

Cysteine aminotransferase has been purified over 300-fold from rat liver mitochondria. Transamination between L-cysteine and 2-oxoglutarate, and the reverse reaction, were observed to be catalyzed by the purified enzyme but inhibited by L-aspartate. The enzyme also catalyzed transamination of alanine, 3-sulfinic acid, aspartic acid, and cysteic acid. A new reaction assay method was devised, contributing an indication that mitochondrial cysteine aminotransferase is identical to mitochondrial aspartate aminotransferase. The latter apparently catalyzed 3 transamination reactions in the cysteine degradation process within mitochondria.