Dipeptidyl carboxypeptidase from human seminal plasma

Dipeptidyl carboxypeptidase (angiotensin I converting enzyme) was purified from human seminal plasma. The apparent relative molecular mass determined by gel filtration on Sephadex G-200 was 330 000. The pI in isoelectric focusing was 4.6--5.0 and the optimum pH 7.7--8.0. The enzyme is activated by chloride. These properties are similar to those reported for the lung enzyme. The specificity is that of a carboxypeptidase releasing dipeptides. A study of different substrates showed the activity to be highest with Z-Leu-Gly-Gly, followed by Z-Phe-His-Leu greater than bradykinin greater than Bz-Gly-Gly-Gly greater than Boc-Phe-Ala-Pro greater than Bz-Gly-His-Leu greater than angiotensin I.