α2antiplasmin activity

α2antiplasmin is the primary inhibitor of plasmin, the enzyme responsible for degradation of fibrin clots. It is cross-linked to fibrin by FXIIIa and inhibits the binding of plasminogen, the pre-cursor of plasmin, to fibrin, and also completely inactivates plasmin itself by forming stable 1:1 complexes.

Inherited deficiency of α2antiplasmin causes a (rare) bleeding disorder due to increased fibrinolysis leading to premature clot lysis before tissue and vessel repair is complete. Homozygous deficiency can lead to severe bleeding symptoms, often presenting in childhood and appearing similar to haemophilia. Initial presentation can be umbilical bleeding, and delayed bleeding is a feature similar to that encountered in FXIII deficiency. Heterozygous individuals have less severe symptoms, the bleeding typically occurring upon challenge, or can be asymptomatic. Acquired deficiency can occur due to consumption, surgery on organs with high content of plasminogen activators or disturbed synthesis.