Secreted tripeptidyl-peptidase which degrades proteins at acidic pHs and is involved in virulence. Release of an N-terminal tripeptide from a polypeptide. Binds 1 Ca(2+) ion per subunit. The predicted genes ARB_04677 and ARB_04678 have been merged. The predicted genes ARB_04677 and ARB_04678 have been merged.