Thiol protease. Acts synergistically with RgpA 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. Inhibited by human histatin-3 1/24 (histatin-5). Belongs to the peptidase C25 family.