Aminopeptidase M (AmM; EC 3.4.11.2) is a membrane-bound peptidase present on renal brush border and vascular plasma membrane. In the present study, AmM, purified from human placenta hydrolyzed alanyl-, leucyl- and arginyle- /beta- naphtylamides at rates of 3.25±0.04, 1.53±0.04 and 0.68±0.02 µmol/min/mg, respectively, exhibited little or no /alpha-glutamyl-, aspartyl-or glycyl-prolyl-naphthylamidase activities (