Aminopeptidase P from bovine lung: solubilization, properties, and potential role in bradykinin degradation

Aminopeptidase P was solubilized from bovine lung by sodium deoxycholate extraction of salt-washed, delipidated lung acetone powders. Hydrolysis of the standard aminopeptidase P substrate, Gly-Pro-Hyp, as well as cleavage of Arg-Pro-Pro and the Arg1-Pro2 bond of bradykinin, co-eluted from a Mono Q anion exchange column and demonstrated identical inhibitory profiles suggesting that all activities were functions of the same enzyme. The metal chelator, 1,10-phenanthroline, completely inhibited activity suggesting that aminopeptidase P is a metallopeptidase. 2-Mercaptoethanol was both a potent and specific inhibitor of the enzyme (at 4 mM). A variety of other peptidase inhibitors showed either no effect or failed to completely inhibit even at high concentrations. The inhibitory profile and substrate specificity differ considerably from previous reports claiming to study the properties of this enzyme. Evidence is provided that aminopeptidase P may have an important role in the pulmonary degradation of the potent vasoactive peptide, bradykinin.