Human factor VIII was purified 350,000-fold (relative to plasma) from a commercial factor VIII concentrate. The procedure used standard protein separation techniques and was performed in the absence of protease inhibitors. The product has a specific activity of 4,900 units/mg, an activity-to-antigen ratio of 75:1 (unit/unit) and no more than 0.1% von Willebrand protein. Electrophoresis of the reduced protein in a denaturing polyacrylamide gel showed a single major band of Mr 100,000. Procoagulant activity was eluted from a nondenaturing gel after electrophoresis in the region of the single major band. Thrombin converted the Mr 100,000 polypeptide to a polypeptide of Mr 75,000. The procoagulant activity was increased 10-fold by thrombin or factor Xa and was completely inhibited by activated protein C or factor VIII inhibitor plasma. This factor VIII preparation consists of a single high molecular weight polypeptide chain and has the highest specific activity thus far reported for human factor VIII.
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Fay et al. (1982) studied this question.