Characteristics of aminopeptidase activity of female housefly reproductive accessory glands

Proteolytic activity was detected in crude extracts of female reproductive accessory glands and the following characteristics of the principal aminopeptidase activities were determined: substrate specificity, pH optima, molecular weights, and effects of inorganic salts. The greatest aminopeptidase activities were found with the β-naphthylamides of: alanine at pH 7.5 and 9.5, leucine at pH 8.0, and methionine at pH 6.5. The methionine-specific activity in the crude extract was stimulated 3 times by 100 mM MgCl2, CaCl2, NaCl, or KCl. Inhibition was noted, and ID50 was determined for each of the other principal substrates with the following salts: CdCl2, CaCl2, ZnCl2, HgCl2, MgCl2, and MnCl2. Molecular weights, estimated on Sephadex G-200 and on Sepharose-6B, were found to be around 210 000 for each of these principal aminopeptidase activities in the crude extract.