Figure 1.

Schematic representation of the plasminogen system. The proenzyme plasminogen (Plg) is converted to the active serine protease plasmin (Plm) by the soluble or membrane bound urokinase-type plasminogen activator (u-PA). Membrane bound u-PA binds to a cellular u-PA receptor (u-PAR). Inhibition of the plasminogen system may occur at the level of the plasminogen activators by plasminogen activator inhibitors (such as PAI-1), or at the level of plasmin by α2-plasmin inhibitor (α2-PI) (also called α2-antiplasmin (α2AP)).