The IDO1 Inhibitor Mechanism of Action (MoA) Assay Kit is designed to determine the mechanism of IDO1 enzyme inhibition (e.g., reversible or irreversible inhibition). The IDO1 Mechanism of Action Assay Kit is simple to use. Inhibitor and enzyme are preincubated allowing the inhibitor to bind. After preincubation, the mixture is diluted into reaction buffer containing the L-tryptophan (L-Trp) substrate and all necessary coupled reaction components. This allows reversible inhibitors to dissociate, while irreversible inhibitors remain associated with the IDO1 enzyme. IDO1 activity is determined by measuring the absorption of the reaction product at =320 – 325 nm.