Involved in the destruction of human tissue by E.histolytica. Can abolish adhesion and degrade matrix proteins such as collagen, laminin and fibronectin. May play an important role in pathogenicity. Hydrolysis of proteins, including basement membrane collagen and azocasein. Preferential cleavage: Arg-Arg-|-Xaa in small molecule substrates including Z-Arg-Arg-|-NHMec. Inhibited by leupeptin and such inhibitors of cysteine proteinases as L-transepoxysuccinyl-L-leucylamido-(4-guanidino)butane, peptidyldiazomethanes, iodoacetic acid and chicken cystatin. kcat is 130 sec(-1) with Z-Arg-Arg-NHMec as substrate and 0.4 sec(-1) with Z-Phe-Arg-NHMec as substrate. Optimum pH is 5.5 with azocasein as substrate, 7 with Z-Phe-Cit-NHMec, and 9.5 with Z-Phe-Arg-NHMec and Z-Arg-Arg-NHMec as substrate. Belongs to the peptidase C1 family.