Hydrolysis of dipeptide derivatives reveals the diversity in the M49 family.

Dipeptidyl peptidase III, a metallopeptidase of the M49 family, was first identified (in the pituitary) by its specific cleavage of diarginyl arylamides, which have been used as preferred assay substrates until now. Here we examined the activity of the yeast and human dipeptidyl peptidase III in parallel. The human enzyme preferred Arg(2)-ß-naphthylamide and showed 620-fold higher k(cat)/K(m) for this substrate. In contrast, the yeast enzyme did not display a preference for any of the X-Arg-ß-naphthylamide analyzed. The replacement of Gly(505) with Asp, resulted in a less active, but more selective, yeast enzyme form. These results indicate diversity in cleavage specificity in the M49 family.