<chemical> A member of the serpin superfamily found in human plasma that inhibits the lysis of fibrin clots induced by plasminogen activator. It is a glycoprotein, molecular weight approximately 70,000 that migrates in the alpha 2 region in immunoelectrophoresis. It is the principle plasmin inactivator in blood, rapidly forming a very stable complex with plasmin.
Pharmacological action: antifibrinolytic agent, serine proteinase inhibitors.