Human Factor IX is a glycoprotein which is synthesized in the liver (1-3). The domain structure of factor IX is similar to that of the other vitamin K dependent coagulation factors. The NH2-terminal region contains 12 g-carboxyglutamic acid (gla) residues which facilitate the calcium dependent binding of factor IX to negatively charged phospholipid surfaces. Two domains which are homologous to epidermal growth factor (EGF) span the region between the NH2-terminal gla domain and the activation peptide (Ala-146 to Arg-180). Factor IX is activated by either factor XIa or the factor VIIa/tissue factor/phospholipid complex. Cleavage at site A yields the intermediate IXa which is subsequently converted to the fully active form IXab by cleavage at site B. The NH2-terminal light chain (GLA and EGF domains) remains covalently attached to the COOH-terminal heavy chain by a disulfide bond. The serine protease catalytic triad (Ser-365, His 221, Asp-269) is located in the heavy chain. Factor IXab is the catalytic component of the ''intrinsic factor Xase complex (factor VIIIa/IXa/Ca2+/phospholipid) which proteolytically activates factor X to factor Xa. IIsoelectric point: 4.2-4.5 (7) Localization: Plasma Plasma Concentration: 4-5ug/ml (1) Mode of Action: Zymogen, precursor to the serine protease Factor IXa Specific Activity: ~100U/mg, 1 unit is equivalent to the Factor IX activity in 1ml of normal plasma Extinction Coefficient (1%, 1cm, 280nm): 13.2 (7) Structure: Single chain, NH2-terminal gla-domain, two EGF domains Percent Carbohydrate: 17% (7) Post-translational Modifications: One b-hydroxyaspartate (9), twelve gla residues (7)
Molecular Weight:
55
Purity:
95%. Human factor IX is prepared from fresh frozen plasma by a combination of conventional procedures and immunoaffinity chromatography (5). Purity is determined by SDS-PAGE analysis and activity is measured using a factor IX clotting assay.
Form:
Supplied in 50% glycerol/H2O.
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