CHEMBL5731170

BACE-1 Ki Assay (BACE-1 HTRF FRET Assay): The following reagents were used in this assay. Na+-Acetate pH 5.0; 1% Brij-35; Glycerol; Dimethyl Sulfoxide (DMSO); Recombinant human soluble BACE-1 catalytic domain (>95% pure); APP Swedish mutant peptide substrate (QSY7-APPswe-Eu): QSY7-EISEVNLDAEFC-Europium-amide.A homogeneous time-resolved FRET assay can be used to determine IC50 values for inhibitors of the soluble human BACE-1 catalytic domain. This assay monitors the increase of 620 nm fluorescence that resulted from BACE-1 cleavage of an APPswedish APPswe mutant peptide FRET substrate (QSY7-EISEVNLDAEFC-Europium-amide). This substrate contains an N-terminal QSY7 moiety that serves as a quencher of the C-terminal Europium fluorophore (620 nm Em). In the absence of enzyme activity, 620 nm fluorescence is low in the assay and increased linearly over 3 hours in the presence of uninhibited BACE-1 enzyme. Inhibition of BACE-1 cleavage of the QSY7-APPswe-Eu substrate by inhibitors is manifested as a suppression of 620 nm fluorescence.Varying concentrations of inhibitors at 3× the final desired concentration in a volume of 10 ul are preincubated with purified human BACE-1 catalytic domain (3 nM in 10 μl) for 30 minutes at 30° C. in reaction buffer containing 20 mM Na-Acetate pH 5.0, 10% glycerol, 0.1% Brij-35 and 7.5% DSMO. Reactions are initiated by addition of 10 μl of 600 nM QSY7-APPswe-Eu substrate (200 nM final) to give a final reaction volume of 30 μl in a 384 well Nunc HTRF plate. The reactions are incubated at 30° C. for 1.5 hours. The 620 nm fluorescence is then read on a Rubystar HTRF plate reader (BMG Labtechnologies) using a 50 milisecond delay followed by a 400 millisecond acquisition time window. Inhibitor IC50 values are derived from non-linear regression analysis of concentration response curves. Ki values are then calculated from IC50 values using the Cheng-Prusoff equation using a previously determined μm value of 8 μM for the QSY7-APPswe-Eu substrate at BACE-1.