Carboxypeptidase B1 is an exopeptidase which specifically cleaves the C-terminal Arg and Lys residues with a preference for Arg. Expressed mainly in pancreas, CPB1 is a useful serum marker for acute pancreatitis and pancreatic graft rejection.Human CPB1 consists of a signal peptide, a pro region, and a mature chain. The purified rhCPB1 corresponds to the pro form, which can be activated by trypsin, the only pancreatic protease capable of generating active enzyme from the zymogen in vitro.