The human DAO biochemical assay was performed using reagents at the following final assay concentrations: 1 nM recombinant full-length human DAO protein, D-Serine at Km concentration (10 mM), 50 µM FAD (excess), 50 µM Amplex Red and 0.1 U/mL HRP in the presence of compound or DMSO vehicle (1%). All reagents were made up in assay buffer containing 20 mM Tris, pH 7.4 + 0.1% BSA. The final assay volume was 25 µL/well.