Coagulation factor II (thrombin) and Coagulation factor X (activated factor X) (Factor IIa (for thrombin), Factor Xa (for activated factor X))

Coagulation factor II (thrombin, IIa) and coagulation factor X (activated factor Xa) are serine proteases that play central roles in the blood coagulation cascade. Factor Xa is generated from its precursor, factor X, through proteolytic cleavage by the intrinsic (factors IXa/VIIIa) or extrinsic (factor VIIa/tissue factor) tenase complexes[2][1]. Factor Xa, in complex with factor Va, calcium, and phospholipids (the prothrombinase complex), catalyzes the conversion of prothrombin (factor II) to the active enzyme thrombin (factor IIa)[3]. Thrombin subsequently cleaves fibrinogen to form fibrin, activates platelets, and further amplifies coagulation and cellular responses via protease-activated receptors (PARs)[4][5]. Both are canonical therapeutic targets in thrombosis and cardiovascular medicine, notably for the prevention and treatment of conditions such as deep vein thrombosis, pulmonary embolism, stroke in atrial fibrillation, and coronary syndromes. Targeting these enzymes with small molecule inhibitors or biologics constitutes the basis for many of the most commonly used anticoagulant drugs[5][2]. Both factors are also implicated in non-coagulation roles, such as inflammation and cardiovascular remodeling, via PAR-mediated signaling[5]. The current entry is *incorrect* as a single canonical target, because "Coagulation factor IIa and Coagulation factor Xa" combines two distinct biology targets, each with separate (albeit interconnected) molecular and therapeutic profiles.

Other names

FIIafactor IIaactivated factor XFXathrombokinaseStuart-Prower factor

Direct inhibition of the catalytic activity of thrombin or factor Xa, leading to reduced conversion of fibrinogen to fibrin, and decreased thrombin generation Indirect inhibition (e.g., via antithrombin potentiation by heparin) Blockade of protease-activated receptor activation, modulating downstream cell signaling