Dipeptidyl peptidase I (, cathepsin C, dipeptidyl aminopeptidase I, dipeptidyl transferase, dipeptide arylamidase I, DAP I) is an enzyme. This enzyme catalyses the following chemical reaction Release of an N-terminal dipeptide, Xaa-Yaa!Zaa-, except when Xaa is Arg or Lys, or Yaa or Zaa is Pro This Cl-dependent, lysosomal cysteine-type peptidase is maximally active at acidic pH. References External links EC 3.4.14