Alfa2antiplasmin

Alpha-2-antiplasmin, also known as alpha-2 antiplasmin or α2AP, is a serine protease inhibitor (serpin) that serves as the principal inhibitor of plasmin, the enzyme responsible for fibrin degradation in the fibrinolytic system. By rapidly inactivating plasmin, α2AP helps regulate clot stability and prevent premature breakdown of clots after hemostasis.

The protein is produced mainly by the liver and circulates in plasma as a single-chain glycoprotein with a molecular weight of about 52 kDa. Its reactive center loop dictates specificity for plasmin. A key feature is the ability of α2AP to be cross-linked into forming fibrin by activated Factor XIII (FXIIIa), which localizes antifibrinolytic protection directly within the clot.

When plasmin is generated at a clot, it encounters α2AP and forms a stable plasmin-α2AP complex that is rapidly cleared from circulation, effectively curtailing fibrinolysis. This inhibition is complemented by the cross-linking of α2AP to fibrin, which further protects the clot from enzymatic breakdown.

Genetics and disorders: Alpha-2-antiplasmin is encoded by the SERPINF2 gene. Deficiency is rare and typically presents with a bleeding tendency, especially after surgery or trauma. Elevated levels of α2AP have been associated with reduced fibrinolysis and may contribute to thrombotic risk or reduced efficacy of thrombolytic therapy in some settings.

Clinical notes: Plasma α2AP levels can be measured as part of fibrinolysis testing. Therapeutic use of α2AP concentrates is limited to replacement in congenital deficiency. In managing bleeding, antifibrinolytic therapies that limit plasmin activity, such as tranexamic acid, are commonly employed.