CHEMBL5732771

DAAO Inhibitory Activity Assay: The DAAO inhibitory activity was measured by assaying the amount of hydrogen peroxide (H2O2) produced by reacting DAAO protein with flavin adenine dinucleotide (FAD) and D-alanine. The amount of H2O2 was determined by measuring the fluorescence generated on conversion of Amplex red (manufactured by Invitrogen Co.) into resorufin by the reaction of H2O2 with horseradish peroxidase (HRP). 4 μL of 4% dimethyl sulfoxide (DMSO) buffer (50 mM sodium phosphate (pH 7.5), 0.02% CHAPS) solution of the test compound was added to 384-well black, low volume plate, a mixed solution (4 μL) of recombinant human DAAO protein (15 nM), which had been expressed in Escherichia coli and purified, and 18 μM FAD was added, and the mixture was incubated at room temperature for 15 min. After incubation, a mixed buffer (4 μL) of 2.25 mM D-alanine, 1.5 U/mL HRP and 150 μM Amplex red was added, the mixture was incubated at room temperature for 30 min, and the fluorescence (excitation wavelength 530 nm, fluorescence wavelength 590 nm) was measured using an Envision plate reader (manufactured by Perkin Elmer Co.). To cross-check the artificial inhibition of Amplex red conversion or the HRP activity inhibition of the test compound, the fluorescence was also measured under the conditions of 30 μM H2O2 addition in the absence of DAAO. Taking the fluorescence value in the absence of the test compound as 100% and the fluorescence value in the absence of DAAO as 0%, the DAAO activity was regarded to have been inhibited when the fluorescence value decreased by 50% in the presence of the test compound, and the concentration of the test compound at that time was taken as the IC50 value (nM).