Factor XI

• OMIM: 264900
• UniProt: P03951
• MGI: 99481

Plasma thromboplastin antecedent (factor XI or short PTA, Eng. Predecessor for the Plasmathromboplastins ), also Rosenthal factor is involved in blood clotting enzyme, specifically a serine proteinase. It is produced by the liver and circulates as a homo- dimer ( via a disulfide bridge covalently linked ) in its inactive form. The monomer has a molecular weight of 80 kDa.

The plasma concentration is 5 mg / liter, the half-life approximately 52 hours.

Genetics

The gene of factor XI in humans is located on chromosome 4, locus q32 - 35th It has a length of 23 Kb and is composed of 15 exons.

Physiology

PTA is the activated Hageman factor (factor XIIa ) or activated by thrombin and then referred to as factor XIa. It is part of the intrinsic pathway of blood coagulation, which comes into action when the Hageman factor and other components encounters negatively charged collagen under the endothelium of the vessel wall.

Factor XIa activates Christmas factor ( factor IX) to factor IXa in which it cleaves an Arg -Ala- Arg -Val and a peptide bond. The Christmas factor then activates the Stuart - Prower factor (factor X).

Diseases

Lack of PTA caused the rare hemophilia C. This occurs frequently (8 %) in Ashkenazi Jews, while it affects only about 1 % of the population in other populations. In this type of hemophilia, spontaneous bleeding is rare, but surgery may cause severe blood loss and therefore require special preparation.

Low -level PTA may also occur in other disorders, such as Noonan syndrome.

Increased PTA level to play a role in the causation of thrombosis, but it is uncertain what factors cause elevated levels and the severity of the procoagulant effect.