In the common pathway, prothrombinase converts prothrombin into which active enzyme?

1. Once factor X is activated by either initial pathway, the common pathway begins. 2. The enzyme prothrombinase converts factor II, the inactive prothrombin, into the active enzyme thrombin. 3. Prothrombin is stored inactive on purpose, since active thrombin circulating freely would clot blood spontaneously. 4. Fibrin is produced one step later, by thrombin acting on fibrinogen, so it is the product of the product. 5. Plasmin belongs to fibrinolysis, the dismantling of the clot rather than its construction. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 18 "The Cardiovascular System: Blood", section 18.5 Hemostasis_