Carboxypeptidase E cleaves C-peptide (Insulin(57-89)) to yield C-peptide (Insulin(57-87))

Stable Identifier
R-HSA-9023159
Type
Reaction
Species
Homo sapiens
Compartment
Locations in the PathwayBrowser
Summation

Carboxypeptidase E (CPE, also called Carboxypeptidase H) cleaves the C-terminal arginine-89 and lysine-88 from the C-peptide (Chen et al. 2001 and inferred from rat Cpe). The reaction occurs in immature secretory granules (Orci et al. 1985)
Overall, proinsulin in proinsulin-zinc-calcium complexes is cleaved by endopeptidases PCSK1 (Prohormone Convertase 1/3) and PCSK2 (Prohormone Convertase 2). The exopeptidase CPE (Carboxypeptidase E, also called Carboxypeptidase H) removes 2 amino acids from the carboxyl termini of the resulting B chain (INS 25-56) and C-peptide (INS 57-87). In the major pathway of processing PCSK1 cleaves between the B chain and the C-peptide, CPE removes two arginine residues from the C-terminus of the B chain, PCSK2 cleaves between the C-peptide and the A chain (INS 90-110), and CPE removes an arginine residue and a lysine residue from the C-terminus of the C-peptide. Unlike the proinsulin-zinc calcium complex, the insulin-zinc-calcium complex is not soluble and forms crystals inside the secretory granules.

Participants
Participant Of
Catalyst Activity
Catalyst Activity
Title
metallocarboxypeptidase activity of CPE:Zn2+ [secretory granule membrane]
Physical Entity
Activity
Inferred From