Michaelis-Menten profiles for cleavage of Aβ1–40 by wild-type NEP and NEPv.

<p>Aβ1<b>–</b>40 cleavage activity was determined at 0.4<b>–</b>50<b> µ</b>M substrate with 40<b> </b>nM wild-type NEP (•) or 10<b> </b>nM NEPv (○). Activity data were normalised to enzyme concentration and plotted against substrate concentration, and the Michaelis-Menten equation was used to fit them. Error bars represent the spread of two replicate data points. NEPv showed <b>∼</b>20-fold increased catalytic efficiency on Aβ1<b>–</b>40 compared to wild-type NEP. The limited solubility of FAM- and biotin-labelled Aβ1<b>–</b>40 in aqueous buffers precluded the use of substrate concentrations above 50<b> µ</b>M in the assay.