Abstract
Histidine-pyruvate aminotransferase and glutamine-phenylpyruvate aminotransferase were purified from rat kidney by the same procedure. The ratio of the two activities remained constant during purification and was unchanged by a variety of treatments of the purified enzyme. Glutamine was found to act as a competitive inhibitor of histidine-pyruvate aminotransferase. These results suggest that rat kidney histidine-pyruvate aminotransferase is identical with glutamine-oxo acid aminotransferase. Identity of the two enzymes in other tissues of rats is discussed.