FRETS‐VWF73, a first fluorogenic substrate for ADAMTS13 assay

Summary A plasma metalloprotease, ADAMTS13, cleaves von Willebrand factor (VWF) multimers and downregulates their activity in platelet aggregation. Functional ADAMTS13 deficiency leads to the accumulation of hyperactive large VWF multimers, inducing a life‐threatening disease, thrombotic thrombocytopenic purpura (TTP). Although measuring ADAMTS13 activity is important in TTP diagnosis, existing methods require time and skill. Here, we report a fluorescence resonance energy transfer (FRET) assay for ADAMTS13 activity. We developed a synthetic 73‐amino‐acid peptide, FRETS‐VWF73. Cleavage of this substrate between two modified residues relieves the fluorescence quenching in the intact peptide. Incubation of FRETS‐VWF73 with normal human plasma quantitatively increased fluorescence over time, while ADAMTS13‐deficient plasma had no effect. Quantitative analysis could be achieved within a 1‐h period using a 96‐well format in commercial plate readers with common filters. The FRETS‐VWF73 assay will be useful for the characterization of thrombotic microangiopathies like TTP and may clarify the importance of ADAMTS13 activity as a predictive marker for various thrombotic diseases.