Potential cleavage sites in the VWF-A2 domain of leukocyte proteases and ADAMTS13. A schematic diagram of the VWF A domains is shown with the peptide bond cleavage sites in the A2 domain shown by arrows for neutrophil elastase, PR3, cathepsin G, ADAMTS13, MMP9, and neutrophils. The cleavage sites were determined by mass spectrometry analysis of the carboxyl terminal fragments of cleaved FRETS-VWF73, and confirmed by amino terminal sequencing of approximately 175 kDa electrophoretic bands of cleaved multimeric VWF under reducing conditions for neutrophil elastase, PR3, and cathepsin G.