Molecular and catalytic properties of rabbit testicular dipeptidyl carboxypeptidase.

Rabbit testicular dipeptidyl carboxypeptidase activity was purified by a procedure exploiting its affinity for N-alpha-[1-(S)-carboxy-3-phenylpropyl]-L-lysyl-L-proline. The molecular, catalytic, and immunological properties of the testicular enzyme are presented and compared with the corresponding properties of pulmonary angiotensin-converting enzyme. Although catalytically similar and immunologically related to pulmonary dipeptidyl carboxypeptidase, the testicular enzyme has a molecular weight (100,000) which is lower by a factor of about one-third and differs in its NH2 and COOH termini. Furthermore, we present evidence that the testicular enzyme is not a post-translation product of the pulmonary type enzyme. These data suggest that testicular and pulmonary dipeptidyl carboxypeptidase are two distinct proteins which are catalytically similar and immunologically closely related.