Activity of IDE and its mutants with amyloid beta peptide and insulin as substrates.

Reactions containing 10 µM Aß1–40 or 10 µM insulin as substrates in 50 mM Tris-HCl buffer, pH 7.4, were incubated at 37°C for 30 to 60 min. Rates were determined by measuring the disappearance of the substrate peak by HPLC as described in Methods. IDEC812S and IDEC819S were used as controls to demonstrate the specificity of effects resulting from mutating Cys 904 and Asn 575. Data is expressed as the mean plus or minus the standard deviation. Each value represents measurements made two to five times.