The most commonly used anticoagulants in clinical practice, warfarin and the heparin series of anticoagulants and fondaparinux, act to inhibit the action of Factor Xa in various degrees. Traditional models of coagulation developed in the 1960s envisaged two separate cascades, the extrinsic (tissue factor (TF)) pathway and the intrinsic pathway. These pathways converge to a common point, the formation of the Factor Xa/Va complex which together with calcium and bound on a phospholipids surface, generate thrombin (Factor IIa) from prothrombin (Factor II). A new model, the cell-based model of anticoagulation appears to explain more fully the steps in coagulation. This model has three stages: 1) initiation of coagulation on TF-bearing cells, 2) amplification of the procoagulant signal by thrombin generated on the TF-bearing cell and 3) propagation of thrombin generation on the platelet surface. Factor Xa plays a key role in all three of these stages.In stage 1, Factor VII binds to the transmembrane protein TF on the surface of cells and is converted to Factor VIIa. The result is a Factor VIIa/TF complex, which catalyzes the activation of Factor X and Factor IX. Factor Xa formed on the surface of the TF-bearing cell interacts with Factor Va to form the  prothrombinase complex which generates small amounts of thrombin on the surface of TF-bearing cells. In stage 2, the amplification stage, if enough thrombin has been generated, then activation of platelets and platelet-associated cofactors occurs. In stage 3, thrombin generation, Factor XIa activates free Factor IX on the surface of activated platelets.
Polymorphisms in Factor X have been associated with an increased prevalence in bacterial infections, suggesting a possible role directly regulating the immune response to bacterial pathogens. Therapeutic use
Factor X is part of fresh frozen plasma and the prothrombinase complex. There are two commercially available Factor X concentrates: "Factor X P Behring" manufactured by CSL Behring, and high purity Factor X Coagadex produced by Bio Products Laboratory and approved for use in the United States by the FDA in October 2015, and in the EU in March 2016, after earlier acceptance by CHMP and COMP.Kcentra, manufactured by CSL Behring, is a concentrate containing coagulation Factors II, VII, IX and X, and antithrombotic Proteins C and S.

Use in biochemistry
The factor Xa protease can be used in biochemistry to cleave off protein tags that improve expression or purification of a protein of interest. Its preferred cleavage site (after the arginine in the sequence Ile-Glu/Asp-Gly-Arg, IEGR or IDGR) can easily be engineered between a tag sequence and the protein of interest. After expression and purification, the tag is then proteolytically removed by factor Xa. Factor Xa
Factor Xa is the activated form of the coagulation factor X, also known as thrombokinase and known eponymously as Stuart-Prower factor. Factor X is an enzyme, a serine endopeptidase, which plays a key role at several stages of the coagulation system. Factor X is synthesized in the liver.