Participation of Factor Va in Prothrombinase: Factor Va, composed of a heavy (VaH) and light (VaL) chain, binds to negatively charged phospholipid membranes and effectively serves as a receptor for membrane bound factor Xa (Xa). The enzyme complex serves to convert the zymogen prothrombin (II) to the active serine protease thrombin (IIa), in a proteolytic event which removes the fragment 1.2 (F1.2) portion of prothrombin. Factor Va is a cofactor for the serine protease factor Xa, and in the presence of calcium ions they collectively assemble on a phospholipid surface to form the prothrombinase complex (1). The prothrombinase complex is responsible for the rapid conversion of prothrombin to thrombin. Factor Va is derived from the pro-cofactor, factor V, upon limited proteolysis by a-thrombin. The thrombin cleavage of factor V liberates two heavily glycosylated activation peptides from the central portion of the molecule which have no cofactor function. Factor Va is comprised of an NH2-terminal derived heavy chain (Mr=94,000) and a COOH-terminal derived light chain (Mr=74,000) which remain associated in the presence of calcium ions. The cofactor binds to phospholipid (cell membrane) surfaces and effectively serves as a receptor for membrane bound factor Xa. Complete assembly of the prothrombinase complex (factor Xa, factor Va, phospholipid, and calcium) results in a 300,000-fold increase in the rate of prothrombin conversion relative to the rate observed with factor Xa alone. The interaction between factor Va and factor Xa is mediated by both the heavy and light chain of factor Va, while the binding of prothrombin to factor Va is mediated solely by the heavy chain. Localization: Plasma and membrane surfaces Mode of Action: Cofactor for factor Xa in the prothrombinase complex Molecular Weight: ~168,000, Based upon the combined molecular weight of the subunits Extinction coefficient: E1%1cm, 280nm=17.4 (3) Structure: Two subunits, Mr~94,000 (heavy chain) and 74,000 (light chain) (4) Percent Carbohydrate: ~8%, Based upon the calculated molecular weight of human factor Va. Storage and Stability: May be stored at 4C for short-term only. Aliquot to avoid repeated freezing and thawing.. Store at -20C. Aliquots are stable for 6 months after receipt at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
Reinheit:
95%. Factor Va is prepared by activating purified factor V with thrombin and is subsequently purified by immunoaffinity chromatography (2). This process results in cofactor preparations which are free of both activation peptides and thrombin. Purity is determined by SDS-PAGE analysis and activity is measured in a factor Va clotting assay.
Formulierung:
Supplied as a liquid in 50% glycerol, 5mM CaCl2.
* Mehrwertsteuer und Versandkosten nicht enthalten. Irrtümer und Preisänderungen vorbehalten
