Enzymatic Degradation of the Factor VIII-Von Willebrand Protein:A Unique Tryptic Fragment with Ristocetin Co-Factor Activity

Highly purified von Willebrand protein was obtained from pooled human cryoprecipitate using polyethylene glycol precipitation followed by agarose gel chromatography, and concentrated by dialysis against 20% polyethylene glycol-20,000. Subsequent partial hydrolysis with trypsin destroyed all of the procoagulant activity and 97% of the ristocetin co-factor activity of the original purified material. Such digests were gel filtered and then analyzed by determinations of biological activities and by SUS-Polyacrylamide gel electrophoresis. All of the ristocetin co-factor activity present in the digest was found in a 100,000 dal ton fragment. Larger fragement thmoecular weights 150,000-260,000 daltons as well as smaller fragments (< 50,000) lacked ristocetin co-factor activity. Fragments smaller than 50,000 dal tons did not react with heterologous antisera. These observations suggest that the ristocetin co-factor activity of the intact von Willebrand molecule is located in one or more specialized regions, partially retained in this unique intermediate-sized tryptic degradation product.

 

Scroll to top

 

 

Scroll to top