In this reaction, all reactants and products are invisible. The heat being evolved is the clue that tells you a reaction is taking place. This is a good example of an exothermic reaction, a reaction in which heat is given off. A lot of reactions are exothermic.
Prothrombinase will cleave prothrombin to make thrombin and thrombin is the enzyme that cuts fibrinogen to make fibrin for clot formation [Blood Clotting: The Basics]. The platelet prothrombinase activity is the same as the activity on TP-bearing cells: itâs formed from Xa and membrane-bound Va.
Thrombin is a serine protease, an enzyme that, in humans, is encoded by the F2 gene. Prothrombin is proteolytically cleaved to form thrombin in the clotting process. Thrombin in turn acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin, as well as catalyzing many other coagulation-related reactions.