F9

This gene encodes vitamin K-dependent coagulation factor IX that circulates in the blood as an inactive zymogen. This factor is converted to an active form by factor XIa, which excises the activation peptide and thus generates a heavy chain and a light chain held together by one or more disulfide bonds. The role of this activated factor IX in the blood coagulation cascade is to activate factor X to its active form through interactions with Ca+2 ions, membrane phospholipids, and factor VIII. Alterations of this gene, including point mutations, insertions and deletions, cause factor IX deficiency, which is a recessive X-linked disorder, also called hemophilia B or Christmas disease. Alternative splicing results in multiple transcript variants encoding different isoforms that may undergo similar proteolytic processing.

Full Name

Coagulation Factor IX

Research Area

Factor IX is a vitamin K-dependent plasma protein that participates in the intrinsic pathway of blood coagulation by converting factor X to its active form in the presence of Ca2+ ions, phospholipids, and factor VIIIa.

Biological Process

Blood coagulation Source: UniProtKB
Proteolysis Source: UniProtKB
Zymogen activation Source: UniProtKB

Cellular Location

Secreted

Involvement in disease

Hemophilia B (HEMB):
An X-linked blood coagulation disorder characterized by a permanent tendency to hemorrhage, due to factor IX deficiency. It is phenotypically similar to hemophilia A, but patients present with fewer symptoms. Many patients are asymptomatic until the hemostatic system is stressed by surgery or trauma. Mutations in position 43 (Oxford-3, San Dimas) and 46 (Cambridge) prevents cleavage of the propeptide (PubMed:12588353, PubMed:2738071, PubMed:3009023, PubMed:8295821, PubMed:9169594, PubMed:9600455, PubMed:25251685). Mutation in position 93 (Alabama) probably fails to bind to cell membranes (PubMed:3790720). Mutation in position 191 (Chapel-Hill) or in position 226 (Nagoya or Hilo) prevent cleavage of the activation peptide (PubMed:6603618, PubMed:8076946, PubMed:12588353, PubMed:2162822, PubMed:25251685, PubMed:2713493).
Thrombophilia, X-linked, due to factor IX defect (THPH8):
A hemostatic disorder characterized by a tendency to thrombosis.
Warfarin sensitivity, X-linked (WARFS):
A condition characterized by sensitivity to warfarin, a drugs used as anti-coagulants for the prevention of thromboembolic diseases in subjects with deep vein thrombosis, atrial fibrillation, or mechanical heart valve replacement. Warfarin sensitive individuals develop bleeding complications when they are given warfarin within the therapeutic ranges.

PTM

Activated by factor XIa, which excises the activation peptide (PubMed:9169594, PubMed:1730085). The propeptide can also be removed by snake venom protease (PubMed:20004170, PubMed:20080729).
The iron and 2-oxoglutarate dependent 3-hydroxylation of aspartate and asparagine is (R) stereospecific within EGF domains.