Peptidase M14 carboxypeptidase subfamily A/B-like; Carboxypeptidase B subgroup
Peptidase M14 Carboxypeptidase B (CPB) belongs to the carboxypeptidase A/B subfamily of the M14 family of metallocarboxypeptidases (MCPs). The M14 family are zinc-binding CPs which hydrolyze single, C-terminal amino acids from polypeptide chains, and have a recognition site for the free C-terminal carboxyl group, which is a key determinant of specificity. Carboxypeptidase B (CPB) enzymes only cleave the basic residues lysine or arginine. A/B subfamily enzymes are normally synthesized as inactive precursors containing preceding signal peptide, followed by a globular N-terminal pro-region linked to the enzyme; these proenzymes are called procarboxypeptidases. The procarboxypeptidase B (PCPB) is produced by the exocrine pancreas and stored as stable zymogen in the pancreatic granules until secretion into the digestive tract occurs. PCPB has been reported to be a good serum marker for the diagnosis of acute pancreatitis and graft rejection in pancreas transplant recipients. this subfamily also includes thrombin activatable fibrinolysis inhibitor (TAFIa), a carboxypeptidase that stabilizes fibrin clots by removing C-terminal arginines and lysines from partially degraded fibrin. Inhibition of TAFIa stimulates the degradation of fibrin clots and may help in prevention of thrombosis.
Comment:Metallocarboxypeptidases share the zinc binding motif HXXE...H, where the zinc ion is penta-coordinated to ND1 atoms of the histidines, OE1 and OE2 atoms of the glutamic acid, and to a water molecule in a slightly distorted tetrahedral manner.
Structure:1KWM: human Procarboxypeptidase B; contacts at 3.5A
Jiyao W et al.(2023). "The conserved domain database in 2023.",