Cleaves a wide range of dipeptides and tripeptides, but does not display activity against larger peptides. May have a role in the survival of F.nucleatum in the subgingival environment of the mouth. Release of the N-terminal residue from a tripeptide. Binds 2 Zn(2+) or Co(2+) ions per subunit. Inhibited by the chelating agents EDTA and 1,10-phenanthroline, by bestatin and amastatin, p-hydroxymercuribenzoate and some divalent cations at high concentration. Optimum pH is 7.5-8. Cell envelope associated. Belongs to the peptidase M20B family.