TDO Reaction Solution is an optimized, proprietary formulation containing all the necessary reaction components for TDO-catalyzed conversion of L-tryptophan (L-Trp) to kynurenine (Kyn) in in vitro enzyme activity assays. This product is intended to be used with the BPS TDO Inhibitor Screening Assay Kit (BPS Cat. #72023) and/or with purified, active TDO, His-tag (BPS Cat. #71195) in combination with 1x TDO Assay Buffer (BPS Cat. #73006).