Factor X, also known by the eponym Stuart–Prower factor, is an enzyme of the coagulation cascade. It is a serine endopeptidase. Factor X is synthesized in the liver and requires vitamin K for its synthesis. Factor X is activated, by hydrolysis, into factor Xa by both factor IX and factor VII with its cofactor, tissue factor. The mature form of Factor X (Factor Xa) is generated by Factor IXa- or Factor VIIa-mediated cleavage at the tripeptide sequence, Arg-Lys-Arg, to yield a disulfide linked dimer. Together with the cofactor Factor Va and Ca2+ on the surface of platelets or endothelial cells, Factor Xa coordinates as part of the prothrombinase complex, which mediates proteolysis of Prothrombin into active Thrombin.
