What is factor VII?

Updated: Feb 05, 2020
  • Author: Bishnu Prasad Devkota, MD, MHI, FRCS(Edin), FRCS(Glasg), FACP; Chief Editor: Eric B Staros, MD  more...
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Answer

Answer

Factor VII circulates as a single-chain zymogen of molecular weight of about 50,000 daltons. It has the shortest half-life of the procoagulant factors, approximately 3-6 hours. [1] The human factor VII gene is located on chromosome 13, very close to the gene for factor X. [1] Embryos deficient in factor VII developed normally without evidence of hemorrhage. Nevertheless, factor VII-deficient newborns sometimes develop fatal intra-abdominal or intracranial hemorrhage. [2]

Factor VII binds to tissue factor. Once bound to its cofactor, factor VII can be activated by a number of different proteases. Carboxylation by vitamin K is necessary to activate this factor. The physiologic activator of factor VII is thought to be factor Xa, although significant auto-activation by factor VIIa can occur. [4] The factor VIIa/TF complex activates both factors IX and X. It is inhibited by tissue factor pathway inhibitor (TFPI) in complex with factor Xa. It is also inhibited by antithrombin (AT), but only in the presence of heparin.

The Food and Drug Administration (FDA) approved recombinant activated factor VII (synthetic vitamin K-dependent protein) for the treatment of bleeding and perioperative management in patients with hemophilia A or B who have developed inhibitors against replacement coagulation factors. It has also been approved for such use in acquired hemophilia, congenital factor VII deficiency, and Glanzmann thrombasthenia with refractoriness to platelets. Recombinant activated factor VII (rFVIIa) binds to exposed tissue factor at the place of tissue and vascular injury. Thrombin generated by this process activates platelets and the coagulation cascade. It has been used in controlling hemorrhage from surgery, trauma, and other causes with success. [5] It has also been found useful in the treatment of obstetrical hemorrhage in women with or without hemophilia.


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