Comparison of phytolacain R, a cysteine protease from Phytolacca americana, with papain.

Nine sites of oxidized insulin B-chain were cleaved by phytolacain R, isolated from pokeweed, after 20 hr of hydrolysis. Five cleavage sites resembled those of papain. Substrate specificity of phytolacain R was similar to that of papain, preferring hydrophobic P2 residues. The activities of fibrin formation and elastin hydrolysis of phytolacain R were higher than those of papain. The amino terminal sequence of phytolacain R, although similar was not identical with that of papain.