Comparison of the activity levels of recombinant human ADAMTS13 and its truncated variants against VWF multimers or human VWF73 fusion peptide. (A) The lengths of the recombinant proteins used in the experiment are depicted against the domain structure of ADAMTS13. (B) The activity levels of each protein against VWF multimers (■) or human VWF73 fusion peptide (▩) are depicted. Recombinant proteins were assayed for activity of cleaving either VWF multimers or human VWF73 fusion peptide. All values were expressed using normal human plasma as the reference. Each column represents the mean and standard deviation of results obtained from 3 lots of the protein. The inset shows a magnification of the results for AD2. AD2 and AD5 were relatively less effective in cleaving VWF73 multimers than cleaving VWF73 peptide (P < .05 and < .001, respectively). No such substrate-dependent difference was observed for AD6 or AD7.