The TDO Fluorogenic Inhibitor Screening Assay Kit is designed to measure enzyme inhibition of tryptophan 2,3-dioxygenase (TDO). The TDO Fluorogenic Inhibitor Screening Assay Kit is simple to use and detects fluorescence at long wavelengths, which minimizes potential errors due to compound interference. In the assay, the inhibitor and enzyme are added to a sample containing L-Trp substrate. After a 1 hour incubation at room temperature, the fluorescence solution is added and incubated at 37°C for four hours. Activity is measured by reading sample fluorescence at λ=510 nm following excitation of the reaction product at λ=400 nm.