Plasmin is an important enzyme () that degrades many blood plasma proteins, most notably fibrin clots. The degradation of fibrin is termed fibrinolysis.

It is a serine protease that is released as plasminogen into the circulation and activated by tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), thrombin, fibrin and factor XII (Hageman factor). It is inactived by alpha 2-antiplasmin, a serine protease inhibitor (serpin).

Apart from fibrinolysis, plasmin proteolyses proteins in various other systems: it activates collagenases, some mediators of the complement system and weakens the wall of the Graafian follicle (leading to ovulation). It cleaves fibrin, fibronectin, thrombospondin, laminin and von Willebrand factor.

Deficiency in plasmin may lead to thrombosis, as clots are not degraded adequately.

External link

Acute phase proteins | Fibrinolytic system | EC 3.4.21

Plasmin | プラスミン