CPB2TAFI

CPB2TAFI, commonly known as thrombin-activatable fibrinolysis inhibitor (TAFI), is a plasma enzyme that modulates fibrinolysis. It is encoded by the CPB2 gene, which produces procarboxypeptidase B2, the zymogen form that circulates in blood and is activated to TAFI.

TAFI activation occurs primarily through the thrombin-thrombomodulin complex on endothelial surfaces; plasmin can also activate procarboxypeptidase B2. The active enzyme, TAFIa, is a zinc-dependent metallocarboxypeptidase that removes C-terminal lysine and arginine residues from partially degraded fibrin and other proteins. This activity reduces binding sites for plasminogen on fibrin, thereby dampening plasmin generation and slowing fibrinolysis. TAFIa is inherently unstable and has a short functional half-life, maintaining tight control over its antifibrinolytic effect.

Genetic variation in CPB2 influences circulating TAFI levels and activity, and multiple studies have explored associations with thrombotic or bleeding disorders, with inconsistent results. Because of its role in regulating clot breakdown, TAFI has been investigated as a potential target for anti-thrombotic therapies, as well as a biomarker in coagulation disorders.

The CPB2/TAFI protein is secreted mainly by the liver and circulates in plasma, functioning as a regulatory component of the fibrinolytic system. It belongs to the metallocarboxypeptidase family and requires zinc for catalytic activity.