The catalytic properties of cathepsin C

Abstract

• 1.

  1. The catalytic properties of the intracellular peptidase cathepsin C (EC 3.4.4.9) were investigated. The enzyme is devoid of the proteolytic activity that had been ascribed to it.

• 2.

  2. Cathepsin C has a very narrow specificity. Its activity is restricted to the removal of N-terminal dipeptide units that meet a number of rigorous requirements, from amides, esters or polypeptides.

• 3.

  3. In transamidation reactions cathepsin C shows a narrow specificity not only for the peptide “donor”—as in its hydrolytic activities—but also for the “acceptor” to which the dipeptide units are transferred.

• 4.

  4. These enzymic properties make a function of cathepsin C in intracellular protein catabolism seem improbable.