Properties and distribution of aminopeptidase and dipeptidyl aminopeptidase III of human erythrocytes.

The catalytic properties of depeptidyl aminopeptidase and aminopeptidase isolated from human erythrocytes, and the distribution of their activities in different blood cells were determined. Dipeptidyl aminopeptidase was shown to be of the dipeptidyl aminopeptidase III type, activated by Co2+ and inhibited by EDTA, pCMB and partially by DFP and leupeptin. Aminopeptidase preferred Lys-, Phe-, ARg-, and Met-2-naphthylamides as substrates. It was activated by Co2+ and inhibited by EDTA amastatin, bestatin and leupeptin. Dipeptidyl aminopeptidase III activity and aminopeptidase activity on arginine-2-naphthylamide was higher in the population of younger red blood cells. The same activities were also found in thrombocytes, mononuclear and polymorphonuclear leukocytes in concentrations higher than those in erythrocytes.