Expression of sialic acid specifically enhances VWF proteolysis by ADAMTS13. To establish the effect of desialylation of VWF on susceptibility to nonspecific proteolysis, VWF was treated with α2-3,6,8,9 neuraminidase and subsequently subjected to cleavage by chymotrypsin (60 U/mg VWF), cathepsin B (4 U/mg VWF), and ADAMTS13 (500nM/mg VWF) at 37°C for 90 minutes. Results are shown as residual collagen binding activity at 90 minutes ± SEM for each of the samples. *P < .05. ***P < .001.