CPE is a carboxypeptidase that cleaves C-terminal amino acid residues and is involved in the biosynthesis of peptide hormones and neurotransmitters, including insulin. It is a peripheral membrane protein. The protein specifically binds regulated secretory pathway proteins, including prohormones, but constitutively secreted proteins. Mutations in CPE are implicated in type II diabetes. Recombinant human CPE protein, fused to His-tag at N-terminus, was expressed in E.coli.