Factor IX of the blood coagulation system: a review.
Factor IX is a factor of the blood coagulation system. Its activation occurs on the surface of phospholipid membranes. It can be activated by the factor VIIa-TF (tissue factor)-Ca2+ complex via an extrinsic pathway and by factor XIa in the presence of Ca2+ via the intrinsic pathway of blood coagulation system activation. The activated factor IXa is a serine proteinase. The main function of the activated factor IXa in complex with factor VIIIa and phospholipids in presence of Ca2+ consists of the activation of factor X. Factor IX is synthesized in the liver and is subject to a number of posttranslational modifications including gamma-carboxylation, beta-hydroxylation, and glycosylation. It forms a subgroup of vitamin K-dependent plasma proteins including factors VII and X and protein C characterized by identical domain structures having high levels of homology. Factor IX consists of an NH2-terminal Gla domain, two epidermal growth factor (EGF)-like domains, and a C-terminal domain containing Ser in its active site. Factor IX deficiency in human plasma results in the disease known as hemophilia B.
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Palladin Institute of Biochemistry, Ukrainian National Academy of Sciences, Kiev, Ukraine.
D000818:Animals; D000990:Antithrombin III / Q000494:pharmacology; D001777:Blood Coagulation / Q000502:physiology*; D010450:Endopeptidases / Q000378:metabolism; D005164:Factor IX / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D015942:Factor VIIa / Q000378:metabolism; D015945:Factor XIa / Q000378:metabolism; D002836:Hemophilia B / Q000097:blood / Q000628:therapy; D006801:Humans; D015394:Molecular Structure; D013925:Thromboplastin / Q000378:metabolism
D000990:Antithrombin III; D005164:Factor IX; D013925:Thromboplastin; D010450:Endopeptidases; D015942:Factor VIIa; D015945:Factor XIa