Transamidation reactions catalyzed by cathepsin C.

Previous publications from this laboratory (l-3) have described the catalysis of transamidation reactions by the proteinases papain, ficin, and crystalline chymotrypsin. In addition, preliminary experiments were reported on replacement reactions catalyzed by beef spleen cathepsin C, an intracellular endopeptidase of animal tissues, which resembles pancreatic chymotrypsin in its specificity. The availability of highly purified preparations of cathepsin C (4) has permitted a closer study of its action in the catalysis of transamidation reactions. In the present communication, it is shown that purified beef spleen cathepsin C catalyzes reactions (cf. Reaction A) in which the amide NH2 of its substrate glycyl-L-phenylalaninamide (GPA) is replaced by one of the following: hydroxylamine, CPA itself, or an amino acid amide (e.g., L-argininamide).