Carboxypeptidase B2/CPB2: Proteins and Enzymes

Carboxypeptidase B2 (CPB2), also known as CPU and TAFI, is a secreted glycoprotein member of the peptidase M14 family of enzymes. It is expressed by hepatocytes (60 kDa) and platelets (50 kDa), with MW differences attributable to glycosylation. CPB2 is cleaved by thrombin and plasmin, generating a 36 kDa, relatively insoluble nonglycosylated enzymatically active fragment (TAFIa). Active CPB2 removes C-terminal Lys residues from fibrin, thereby interrupting plasmin generation and promoting fibrin polymerization. CPB2 contains a prosequence (aa 23-114) and an active fragment (aa 115-423) that acts on C-terminal Lys or Arg residues.