Plasminogen is synthesized in the liver as the zymogen precursor of Plasmin, the main enzyme in the fibrinolytic system. Kringle regions 1 & 5 of Plasminogen bind to fibrin in order to localize fibrinolysis and for fibrin to serve as a cofactor in the activation of the zymogen to the active serine protease, Plasmin. Endogenous activators of plasminogen include tissue plasminogen activator (tPA) and Urokinase, or the exogenous activator, Streptokinase. Plasmin can degrade both Fibrinogen and fibrin into soluble products that can be cleared. One of these degraded products is the fragment D-dimer. The slide show entitled Fibrinolytic Pathway shows how Plasminogen participates in fibrinolyisis.
