Physiology, Factor V

Factor V is a glycoprotein that contributes to both procoagulant and anticoagulant function. This function is determined by which enzymes are present that can modify factor V. Factor V gets modified by activated factor X, thrombin, and activated protein C (aPC). Factor V plays a part in the common pathway of the coagulation cascade. In the coagulation cascade, factor V forms a prothrombinase complex with factor X. This prothrombinase complex aids in developing a fibrin and platelet clot and helps to stop bleeding. The coagulation cascade consists of an intrinsic, extrinsic, and common pathway. The cascade involves the activation of clotting factors through the action of serine proteases. Some of these factors will bind to form complexes that can then act as proteases, usually, a serine protease which activates more clotting factors downstream. Inactive clotting factors are always present at some level in the plasma, and contribute to the coagulation cascade when they are activated. The coagulation cascade ultimately concludes in the production of a fibrin clot, which aids in hemostasis to prevent continuing bleeding. The coagulation cascade contributes to hemostasis, the normal functioning of the body to produce a clot in response to injury. Imbalance of the coagulation cascade or loss of regulation can lead to hemorrhage or thrombosis. Thrombosis is a pathological situation where a clot forms where it is not needed and can instead block blood flow and cause ischemia.