Definition: A plasma protein that is the inactive precursor of thrombin. It is converted to thrombin by a prothrombin activator complex consisting of factor Xa, factor V, phospholipid, and calcium ions. Deficiency of prothrombin leads to hypoprothrombinemia.
a blood coag factor; an enzyme precursor
Other names Factor II; Coagulation Factor II; II, Coagulation Factor; Factor, Differentiation Reversal; Factor II, Coagulation; Differentiation Reversal Factor; Blood Coagulation Factor II