Nepenthesin

Nepenthesin (also spelled nepenthacin or nepenthasin) is an aspartic protease of plant origin that has so far been identified in the pitcher secretions of Nepenthes and in the leaves of Drosera peltata. It is similar to pepsin, but differs in that it also cleaves on either side of Asp residues and at Lys┼Arg. While more pH and temperature stable than porcine pepsin A, it is considerably less stable in urea or guanidine hydrochloride. It is the only known protein with such a stability profile.