A vitamin K-dependent glycoprotein containing 11 Gla residues that participates in the common pathway of coagulation. FX is synthesized in the liver and secreted into blood as a precursor to a serine protease (FXa). The conversion of FX to FXa involves a single peptide bond whether brought about by the concerted actions of FIXa, FVIIIa, phospholipid & calcium (tenase complex) or by the FVIIa / Tissue Factor complex. The latter reaction gives rise to an initial burst of Thrombin whereas the tenase complex formed via FIXa brings about a subsequent explosive generation of Thrombin. The slide Coagulation Pathways (All Components) shows how FX relates to the other coagulation factors. See also the slide shows entitled Tissue Factor Pathway (Extrinsic) with Common Pathway (PT) and Intrinsic Pathway-APTT.
