THROMBIN

Thrombin is the last enzyme in the clotting cascade functioning to cleave fibrinogen to fibrin and potentiates the procoagulation process by activating factors V, VIII, XI, and XIII. Conversely, thrombin aids the anticoagulant process by activating protein C. Activated protein C inhibits activated factors V and VIII ultimately down-regulating further thrombin production. Thrombin is often used as a potent platelet activator in vitro. Platelet responses to thrombin are mediated through protease-activated receptors (PARs). Thrombin-mediated signaling regulates a diverse range of metabolic processes including activation of phospholipases in platelets, endothelial cells, and cardiac myocytes.