BASIC-AMINO-ACIDS PREFERRING BROAD SPECIFICITY AMINOPEPTIDASE FROM HUMAN ERYTHROCYTES

An aminopeptidase hydrolyzing 2-naphthylamides of Lys, Arg, Leu, Met, Phe and Tyr, as well as different di- to tridecapeptides, was purified from the cytosol of human erythrocytes. The enzyme showed preference for Lys and Arg at N-terminus, as proline and D-amino acids were nonpermissive at P1' site. Higher affinity for oligopeptides than for aminoacyl naphthylamides was observed. Among the substrates were Lys-bradykinin, angiotensin III, thymopentin and enkephalins. Aminopeptidase was shown to be a monomeric protein of Mr approximately 110000 and of pI approximately 4.8, activated by Co2+ and inhibited by EDTA, pHMB, amastatin, bestatin and puromycin. The isolated enzyme could be classified as cytosolic, Lys(Arg) preferring, broad specificity aminopeptidase.