Coagulation factor Va and Coagulation factor VIIIa (Factor Va (FVa) and Factor VIIIa (FVIIIa))

Coagulation factor Va (FVa) and coagulation factor VIIIa (FVIIIa) are homologous glycoproteins that act as rate-enhancing cofactors in the coagulation cascade. Upon activation by proteolytic cleavage, FVa partners with factor Xa to form the prothrombinase complex, catalyzing the conversion of prothrombin into thrombin[1][3]. FVIIIa functions in the intrinsic tenase complex with factor IXa, dramatically increasing the enzymatic activation of factor X[2][3][7]. Both factors, when activated, bind to negatively charged phospholipid membranes and facilitate rapid clot formation, with their activity finely regulated by activated protein C and its cofactors, including protein S and intact factor V[4][6][7]. Deficiency or dysfunction leads to serious bleeding disorders—hemophilia A for factor VIII and parahemophilia for factor V—while excessive activity predisposes to thrombotic disease[5]. They are therapeutic targets for both clotting factor replacement in bleeding disorders and anticoagulant strategies in thrombotic conditions.

Other names

Activated factor VActivated factor VIIIFVaFVIIIa

Enzymatic degradation by activated protein C (APC)[4][6][7]; Cofactor replacement (therapeutic infusion)[5]; Inhibition by specific antibodies or APC-mimetics (proposed/experimental)[7]