Prothrombin (Factor 2 in the coagulation cascade) is proteolytically cleaved at two sites by Factor Xa to form thrombin (Factor IIa) in an important step of the coagulation cascade which ultimately results in the stemming of blood loss. Thrombin being the single most important constituent of the coagulation cascade in terms of its feedback activation roles. Prothrombin also plays a role in maintaining vascular integrity during development and postnatal life. Mutations in Prothrombin lead to various forms of thrombosis and dysprothrombinemia. Prothrombin is a 72 kDa blood clotting glycoprotein formed by and stored in the Liver. Prothrombin is present in the blood plasma and is converted to the key blood clotting agent thrombin, when blood vessels are damaged. Factor VII, another important haemostasis protein can be converted to VIIa by Factor IXa or Thrombin.Synonyms: Coagulation factor II