Plenary paper Partial amino acid sequence of purified von Willebrand factor–cleaving protease

(vWF-cp) is responsible for the continu-ous degradation of plasma vWF multi-mers released from endothelial cells. It is deficient in patients with thrombotic thrombocytopenic purpura, who show un-usually large vWF multimers in plasma. Purified vWF-cp may be useful for replace-ment in these patients, who are now treated by plasma therapy. In this study, vWF-cp was purified from normal human plasma by affinity chromatography on the IgG fraction from a patient with autoanti-bodies to vWF-cp and by a series of further chromatographic procedures, in-cluding affinity chromatography on Pro-tein G, Ig-TheraSorb, lentil lectin, and heparin. Four single-chain protein bands, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis un-der nonreducing conditions, showed M