Naphthylamidase activity of Leptospira.

Extracts of 18 serotypes of the genus Leptospira were found to possess naphthylamidase activity, and differences in the pathogenic and saprophytic strains were noted. The former exhibited a preference for the leucyl naphthylamide substrate, whereas the latter demonstrated greater hydrolysis of alanyl naphthylamide. With the leucyl naphthylamide as substrate, pathogenic strains showed 10 to 20 times higher naphthylamidase activity than saprophytic strains. Optimal temperature and pH for enzymatic hydrolysis also differed between pathogenic and saprophytic strains. Maximal enzymatic activities for pathogenic and saprophytic naphthylamidases were 41 and 37 C, respectively, at pH 8.0 to 8.5. The pH and temperature optima suggested that the leptospiral enzyme activity was not leucine aminopeptidase.