Purification and characterization of human factor IX

Abstract Human Factor IX has been purified from plasma by a procedure involving DEAE-Sephadex chromatography, affinity chromatography on heparin-Sepharose gel and gel filtration on Sephadex G-200. The final preparation was homogeneous according to a number of criteria and the specific activity corresponded to a 12 000 fold purification from plasma. The molecular weight was 72000 and only tyrosine was found as the N-terminal amino acid. The amino acid composition resembled that of prothrombin. The carbohydrate content was 22.8 %. No change in molecular weight was observed upon polyacrylamide gel electrophoresis in 8 M urea containing mercaptoethanol indicating that Factor IX is a single polypeptide chain crosslinked by disulphide bonds.