Factor V
Biochemistry
| Synonym | Accelerin |
|---|---|
| Molecular mass | 350 000 Da |
| Synthesis | Liver, megakaryocytes, endothelial cells |
| Half life | 12 - 15 hours |
| Plasma concentration | 4 - 14 mg/l |
| Normal range | 60 - 120% or 0.6 - 1.2 U/ml |
As cofactor in the prothrombinase complex, the activated form of factor V accelerates the activation of prothrombin to thrombin by factor Xa. The activation of factor V to factor Va can be effected by thrombin, factor Xa and certain snake venoms such as the Russell’s Viper Venom (RVV). Apart from the procoagulant effect of factor Va, factor V is involved as a cofactor together with protein S in the anticoagulant activity of activated protein C (APC).
Clinical significance
A homozygous hereditary factor V deficiency is very rare, whereas the heterozygous form is often observed. Apart from a true deficiency also altered factor V molecules (dysfunctional forms) exist. An acquired factor V deficiency occurs as a result of hepatic disease, DIC, hyperfibrinolytic conditions and chronic myeloid leukemia. Increased factor Va concentrations as a result of thrombin activation can be observed during phase I of DIC, in acute thrombosis, in postoperative phases and after inflammation.
Indication
- Diagnosis and monitoring of DIC
- Suspected hereditary factor V deficiency in hemorrhage of unknown cause
- Suspected factor V inhibitors
- Suspected pseudo homozygous APC Resistance due to combined FV deficiency and FV:Q506
Literature
- Roberts HR, Foster PA. Inherited disorders of prothrombin conversion. In Colman RW, Hirsh J, Marder VJ, Salzman EW: Haemostasis and Thrombosis. Basic Principles and Therapy, 2 nd ed. Lippincott, Philadelphia, 162, 1987.
- Ortel TL, Kane WH. Factor V. In: High KA, Roberts HR (eds.) Molecular Basis of thrombosis and hemostasis. New York, Marcel Dekker 119-146, 1995.
- Mann KG et al. Cofactor proteins in the assembly and expression of blood clotting enzyme complexes. Ann Rev Biochem 57, 915-956, 1988.
- Guasch JF et al. Molecular characterization of a type I quantitative factor V deficiency in a thrombosis patient that is pseudohomozygous for activated protein C resistance. Thromb Haemost 77, 252-257, 1997.
- Kalafatis M et al. Phenotype and genotype expression in pseudohomozygous factor V Leiden. The need for phenotype analysis. Arterioscler Thromb Vasc Biol 19, 336-342, 1999.
- Hoekema L et al. Human Factor Va1 and Factor Va2: Properties in the Procoagulant and Anticoagulant Pathways. Biochemistry 36, 3331-3335, 1997.