Membrane-bound factor Xa catalyzes the activation of small amounts of thrombin. The amino terminal portion of prothrombin is released as an activation peptide, which can be cleaved further by activated thrombin. Neither the full-length activation peptide nor its cleavage products have known functions.Factor Xa (aka Factor X heavy chain), a cleavage product of coagulation factor X (F10), is a vitamin K-dependent glycoprotein able to convert prothrombin to thrombin during the blood clotting process. Factor Xa is a target for direct oral anticoagulant (DOAC) drugs that are direct factor Xa inhibitors (the so-called 'xabans') and used in the treatment and prevention of thromboembolic disorders (Galanis et al. 2014).