Thiol protease. Acts synergistically with RgpB to catalyze the maturation of fimbrial subunits, such as FimA (By similarity). Its proteolytic activity is a major factor in both periodontal tissue destruction and in evasion of host defense mechanisms (Probable). Hydrolysis of proteins and small molecule substrates, with a preference for Arg in P1. Requires cysteine for activation and Ca(2+) and/or Mg(2+) for stabilization. It is stimulated by glycine-containing dipeptides. It is resistant to inhibition by proteinase inhibitors in human plasma. Belongs to the peptidase C25 family.