This 402-residue serine protease inhibitor, or serpin (MW = 45074 g/mol; Abbreviation: PAI-1) binds to and inhibits plasminogen activators-tissuetype plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). This inhibition reduces plasmin production and suppresses dissolution of fibrin clots. Elevated PAI-1 levels correlate with an increased cardiovascular disease risk, a behavior that has also been linked to obesity and metabolic syndrome. Pharmacological suppression of PAI-1 is a likely way to prevent or treat vascular disease. Reduced PAI-1 levels may result in increased fibrinolysis and an associated bleeding diathesis. PAI-1 was initially identified in the 1980s, and the first reported case of PAI-1 deficiency appeared in 1989. Unambiguous proof that PAI-1 deficiency as a cause of a bleeding disorder has been rare, but use of selective PAI inhibitors (See PAI-749) may clarify this point. Because of lack of standardized commercially available PAI-1 activity assay sensitive in the lowest range, the true prevalence of this rare condition has yet to be established.
