Review of the Structure and Function of Factor V in Blood Coagulation

Blood coagulation involves the serial activation of plasma serine protease precursors (zymogens) by limited proteolysis, to result in the formation of thrombin. The assembly of the prothrombinase complex is essential for rapid thrombin generation. Thrombin amplifies its own production, by activating platelets and the procofactors VIII and V. Activated factor V is a cofactor protein that accelerates the production of thrombin by prothrombinase, an enzyme complex composed of factor Va, factor Xa, prothrombin, calcium ions, and a negatively charged phospholipid membrane. The activity of prothrombinase is regulated to ensure that adequate, but limited levels of thrombin are generated. In turn, the functions of factor Va are regulated by the balance between factor V activation (by thrombin or factor Xa) and factor Va inactivation (by APC and protein S). This review outlines current knowledge on factor V, including its gene, structure, biosynthesis, and its pro- and anti-coagulant roles in blood coagulation.