Prothrombinase complex

Prothrombinase is a macromolecular enzyme complex essential for blood coagulation. It catalyzes the conversion of prothrombin (coagulation factor II) into active thrombin (factor IIa), which then converts fibrinogen into fibrin and activates platelets—key steps in forming a stable blood clot. The prothrombinase complex is composed primarily of two proteins: activated factor V (factor Va) as a cofactor and activated factor X (factor Xa) as the serine protease. These components assemble on negatively charged phospholipid membranes in the presence of calcium ions. The efficiency and specificity provided by this membrane-bound assembly are critical for rapid clot formation at sites of vascular injury. The central role played by prothrombinase in hemostasis makes it an important therapeutic target for anticoagulant drugs used to treat or prevent thrombosis. Inhibitors that block either component—especially direct oral anticoagulants against factor Xa—effectively reduce thrombus formation but carry an increased risk for bleeding complications due to impaired clotting ability. No evidence suggests that "prothrombinase" is misspelled or otherwise incorrect; it refers specifically to this well-characterized enzyme complex involved in blood coagulation.

Other names

ProthrombinaseProthrombinase complexFactor Xa–Factor Va complex

Inhibition of factor Xa activity to prevent formation of the prothrombinase complex and subsequent thrombin generation