Factor Xa (FXa) is the activated form of the coagulation factor X (Stuart-Power factor, thrombokinase, prothrombinase, thromboplastin, E.C.3.4.21.6). Factor X, a serine endopeptidase, plays an important role at several stages of the coagulation pathway. It acts by converting prothrombin into active thrombin by complexing with activated co-factor V in the prothrombinase complex. Unfractionated heparin and various low molecular weight heparins bind to plasma cofactor Antithrombin to inactivate several coagulation factors including factor Xa. Assay Genie's Factor Xa inhibitor screening kit utilizes the ability of Factor Xa to cleave a synthetic substrate thereby releasing a fluorophore, AMC, which can be quantified by a fluorescence reader. In the presence of an inhibitor, the extent of the cleavage reaction is reduced or completely abolished. The loss in the fluorescence intensity can be correlated to the amount of inhibitor present in the assay solution. The Factor Xa Inhibitor Screening Kit is a simple, straightforward, high-throughput assay to screen Factor Xa inhibitors.

Figure: (a) Inhibition of FXa activity by FXa Inhibitor (GGACK Dihydrochloride). (b) FXa activity was measured in plasma samples in the presence and absence of FXa Inhibitor (GGACK Dihydrochloride). S = Substrate, I = Inhibitor. Assays were performed following the kit protocol.