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Coagulation Factor V

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Haematologic Technologies, Inc.

57 River Road

Essex Junction, VT USA

Tel: 802.878.1777

Fax: 802.878.1776

Email: hti@haemtech.com

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ACTIVATION OF FACTOR V BY ALPHA-THROMBIN.  The activation of single chain factor V (330,000) by alpha-thrombin is represented.  Arrows indicate the site at which factor V is cleaved by thrombin to yield two activation peptides (71,000 and 120,000), in addition to the heavy (94,000) and light (74,000) chains which form Va.  The heavy and light chains of factor Va remain non-covalently associated in the presence of calcium ions.

Factor V is a large, single chain, plasma glycoprotein which is an essential component in the blood coagulation cascade (1). During coagulation, the procofactor, factor V, is converted to the active cofactor, factor Va, via limited proteolysis by the serine protease alpha-thrombin (illustrated above), and less efficiently by factor Xa. The active cofactor is composed of an NH₂-terminal derived heavy chain (Mr=94,000) and a COOH-terminal derived light chain (Mr=74,000) which remain non-covalently associated in the presence of calcium ions. Factor Va serves as a cofactor for the serine protease factor Xa. Factor Va and Xa assemble on a phospholipid surface in a non-covalent and calcium ion-dependent manner, to form the prothrombinase complex. The prothrombinase complex is responsible for the rapid conversion of the zymogen prothrombin to the active serine protease, alpha-thrombin. Assembly of the prothrombinase complex increases the rate at which prothrombin is converted to thrombin by nearly 300,000-fold relative to the rate with factor Xa alone. Down regulation of the prothrombinase complex is accomplished partly through the inactivation of factor Va by activated protein C.

Human factor V is prepared from fresh frozen human plasma using immunoaffinity chromatography as described by Katzmann and coworkers (2). Bovine factor V is prepared from fresh bovine plasma using conventional chromatographic techniques as described by Nesheim and coworkers (3). Purified factor V is supplied in 50% glycerol (vol/vol), and should be stored at -20°C. Purity is determined by SDS-PAGE analysis and activity is measured in a factor V clotting assay. 

Properties of Factor V

*determined for bovine factor V
**determined for human factor V
***based upon the calculated molecular weight of human factor V

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References 
1. Mann, K.G., et al., Ann. Rev. Biochem., 57, 915 (1988). 
2. Katzmann, J.A., et al., Proc. Natl. Acad. Sci. USA, 78, 162 (1981). 
3. Nesheim, M.E., et al., J. Biol. Chem., 254, 508 (1979). 
4. Tracy, P.B., et al., Blood, 60, 59 (1982). 
5. Nesheim, M.E., et al., Methods Enzymol., 80, 249 (1981). 
6. Jenny, R.J., et al., Proc. Natl. Acad. Sci. USA, 84, 4846 (1987).

 Please inquire about products not listed.  We can also custom purify proteins from other species.