10 µL of a working solution containing 125 µM Amplex Red and 0.25 U/mL HRP (A22188, ThermoFisher Scientific) in assay buffer was then added to all the wells. The reaction was initiated by the addition of 5 µL of 50 mM D-Serine (S4250, Sigma-Aldrich) to all the wells. The plate was incubated for 4 hours in the dark at 25˚C before measuring fluorescence in each well using the Envision plate reader with excitation at 530 nm and emission at 595 nm. Concentration response curves were generated using ActivityBase (IDBS). IC50 values were determined by plotting % Inhibition vs Log10 compound concentration using a sigmoidal fit with a variable slope (four parameter fit).