Thrombin (凝血酶)

Thrombin is a Na⁺-activated, serine protease which is activated by the enzymatic cleavage of two sites on prothrombin by activated Factor X. Thrombin exists in two allosteric forms, slow (S) and fast (F), target toward anticoagulant and procoagulant activities.

Thrombin is the main effector protease in primary hemostasis by activating platelets and plays a key role in secondary hemostasis. Besides its well-known functions in hemostasis, thrombin also plays a role in various non-hemostatic biological and pathophysiologic processes, predominantly mediated through activation of protease-activated receptors (PARs). PAR-1, PAR-3, and PAR-4 are cleaved by thrombin, whereas PAR-2 is cleaved by trypsin. Thrombin also plays a crucial role in the migration and metastasis of human cancer cells.