CHARACTERIZATION OF A NOVEL PHENYLALANINE-SPECIFIC AMINOPEPTIDASE FROM SCHIZOPHYLLUM-COMMUNE

An aminopeptidase (APF1) with high specificity for phenylalanine and t yrosine in the active site P-1 position was purified from mycelial ext racts of the wood-decaying basidiomycete Schizophyllum commune. A two- dimensional preparative electrophoretic scheme resulted in a 60-fold p urification of the enzyme, which was found to have an M(r) of approxim ately 60 kDa by size exclusion chromatography. SDS-PAGE resolved two c losely migrating subunits of approximately 30 and 31 kDa. Its pi was f ound to be 5.5 and its activity optimum was pH 6.5. Of 11 aminoacyl-p- nitroanilide (-pNA) substrates tested, activity was found only against Phe-pNA. APF1 also showed activity against Phe-beta-naphthylamide (-b eta NA) and Tyr-beta NA; however, the activity against Tyr-beta NA was less than one third of that against Phe-beta NA. No other AA-beta NA substrates were hydrolysed. APF1. hydrolysed a variety of dipeptides w ith Phe in the P-1 position; the amino acid in the P-1' position affec ted the rate. No activity was found against dipeptides where Phe was n ot the N-terminus nor against substrates that were N-blocked. APF1 was partially inhibited by 1,10-phenanthroline, and this inhibition was r eversible by the addition of Zn2+.