Thrombin from Bovine 5ku

α-Thrombin is a trypsin-like serine protease involved in a multitude of processes in the human body. Thrombin generation is the result of limited proteolysis of the vitamin K-dependent zymogen prothrombin. Thrombin is the last enzyme in the clotting cascade functioning to cleave fibrinogen to fibrin which forms the fibrin gel of a hemostatic plug or a pathologic thrombus. In addition, thrombin potentiates the procoagulant process by activating Factors V, VIII, XI and XIII. Thrombin is prepared from fresh bovine plasma by an ion exchange method. Fibrinogen is removed from the prothrombin complex by precipitation. The concentrated prothrombin complex is then activated by beef thromboplastin and calcium. The thrombin solution is clarified by centrifugation and filtration and then lyophilized. Serine protease that selectively cleaves Arg-Gly bonds in fibrinogen to form fibrin and fibrinopeptides A and B. The unit defined by the U.S. standard and is approximately equal to the stated unitage. A U.S. unit is defined as the amount required to clot 1 mL of standardized fibrinogen solution in 15 seconds. Approximately 2 U.S. units are required to clot 1 ml of oxalated human plasma in the same period of time. U.S units = NIH units.