BABOON (PAPIO-URSINUS) CATHEPSIN-L - PURIFICATION, CHARACTERIZATION AND COMPARISON WITH HUMAN AND SHEEP CATHEPSIN-L

Cathepsin L was purified from the liver of a higher primate, the baboo n (Papio ursinus), largely in a single chain form and in the form of p roteolytically active complexes with an endogenous cystatin, This mimi cs the situation found in both human and sheep livers, Both forms of c athepsin L were active at physiological pH, Physicochemical characteri zation and N-terminal amino sequencing of baboon cathepsin L showed a close relationship with the human enzyme. Cystatins with characteristi cs similar to those found for stefins A and B could also be purified f rom baboon livers, Proteolytically active, SDS-stable complexes could be shown to form in vitro with the molecules characterized as stefin B , but not with stefin G type cystatins, The non-inhibitory complexes c ould be shown to require less cysteine for activation than free cathep sin L and this, together with the above result, might indicate that a sulfhydryl interchange mechanism is responsible for the formation of c ovalent, non-inhibitory complexes.