factor Xa


fac·tor Xa

(fak'tŏr) The active form of factor X; it is formed from factor X by limited proteolysis via factor VIIa and tissue factor (extrinsic pathway) or factor IXa, VIIIa (intrinsic pathway). Factor Xa forms a complex with factor Va, phospholipid, and calcium to convert prothrombin to thrombin.