Comparison of Factor VIII-Related von Willebrand Factor Proteins Prepared From Human Cryoprecipitate and Factor VIII Concentrate

Abstract

Both commercial factor VIII concentrate and cryoprecipitate have factor VIII coagulant activity and factor VIII antigen (VIIIR:Ag), but the concentrate lacks the von Willebrand activity (VIIIR:WF) found in the cryoprecipitate. In an effort to find a possible cause for this anomaly we compared the structures of VIIIR:WF proteins responsible for the VIIIR:Ag and VIIIR:WF activities obtained from the two sources. Samples of cryoprecipitate and concentrate were chromatographed on agarose gel, and the resultant VIIIR:WF protein-rich void volume fractions were analyzed by first- and second-dimension sodium dodecyl sulfate gel electrophoresis. Proteins were first separated on a 1.5% polyacrylamide–0.5 % agarose gel and then reduced and electrophoresed into a 3% polyacrylamide-0.5 % agarose gel. VIIIR:WF protein from both cryoprecipitate and concentrate was multimeric, with polymers composed of Mr = 2.4 × 10 5 subunits. However, the multimers of the VIIIR:WF proteins from the two sources differed in average molecular weight and structure. Cryoprecipitate VIIIR:WF multimers were predominantly in the molecular weight range above 5 × 10 5 d and were uniformly separated from each other by increments of Mr = 6.5 × 10 5 . In contrast, concentrate VIIIR:WF multimers were relatively smaller, predominantly in the molecular weight range from 1.4 × 10 6 d to 5 × 10 6 d. The polymeric bands were separated from each other by spaces equivalent to approximately Mr = 5 × 10 5 alternating with distances of Mr = 2.5 × 10 5 . These differences in molecular weight and structure are possible causes for the functional property demonstrated here that VIIIR:WF protein from cryoprecipitate had 2.6 times more VIIIR:WF activity par Mr = 2.4 × 10 5 subunit than VIIIR:WF protein from concentrate.