Coagulation factor V (activated), Coagulation factor VIII (activated) (Factor Va (FVa), Factor VIIIa (FVIIIa))

Coagulation factor Va and coagulation factor VIIIa are activated forms of blood coagulation cofactors that serve as essential non-enzymatic activators within the clotting cascade. Factor Va associates with factor Xa to form the prothrombinase complex, drastically enhancing the rate of prothrombin conversion to thrombin, whereas factor VIIIa binds factor IXa to form the intrinsic tenase complex, amplifying the conversion of factor X to its active form. Both proteins are structurally homologous multidomain glycoproteins requiring membrane binding and metal ions for proper function, and mutations or acquired deficiencies in their genes lead to significant bleeding disorders (hemophilia for FVIII, parahemophilia for FV). Therapeutically, both are key targets for replacement therapy, bypassing strategies, and inhibitor interventions in various coagulopathies[4][2][1][3].

Other names

Factor V activated (FVa)Factor VIII activated (FVIIIa)Proaccelerin (for Factor V)Antihemophilic factor (for Factor VIII)Labile factor (for Factor V)

Cofactor activity accelerates proteolytic activation of prothrombin (for FVa) or factor X (for FVIIIa). Replacement therapies supplement deficient factor VIII or V in bleeding disorders. Inhibitors block cofactor function, reducing thrombin formation (used to treat thrombosis).