Prothrombinase

Prothrombinase is an enzyme complex that converts prothrombin to thrombin in the coagulation cascade. It is formed on the surface of activated platelets and consists of the serine protease factor Xa, and factor Va, bound to the platelet surface via calcium ions.

Structure

The prothrombinase complex is composed of the enzyme factor Xa, and the cofactor factor Va. The complex assembles on negatively charged phospholipid surfaces in the presence of calcium ions. Factor Xa is the enzyme component of the complex, and factor Va is the cofactor.

Function

The primary function of the prothrombinase complex is to convert prothrombin to thrombin in the coagulation cascade, which is a crucial step in blood clotting. The complex achieves this by cleaving two peptide bonds in prothrombin.

Clinical significance

Defects in the prothrombinase complex can lead to a variety of bleeding disorders. For example, deficiencies in factor X or factor V can result in hemophilia-like symptoms. In addition, the complex is a target for anticoagulant drugs, such as direct factor Xa inhibitors.

See also

• Coagulation
• Factor X
• Factor V
• Thrombin
• Prothrombin

References

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