Fig. 1

Schematic diagram of the main mechanisms of the fibrinolytic system and the target site of tranexamic acid (TXA). Lysine binding sites located within the second kringle domain of tPA, and in 4 of the 5 kringle domains of plasminogen can bind to exposed lysine residues on the fibrin surface. This interaction can be inhibited physiologically by Thrombin activatable fibrinolysis inhibitor (TAFI) or pharmacologically by competitive inhibition by the lysine analogue, TXA. The juxtaposition of tPA and plasminogen on the clot surface permits plasmin generation and subsequent fibrinolysis and the formation of fibrin degradation products. Key modulators of this process include plasminogen activator inhibitor-1, PAI-1 (and to some extent, PAI-2) that inhibit both tPA and uPA, and antiplasmin that specifically inhibits plasmin activity. Plasmin can also be inhibited by other molecules including C1-inhibitor (C1-INH) or by alpha2 macroglobulin (A2M)