D-Kynurenine is an antagonist of hydroxycarboxylic acid receptor 3 HCA3/GPR109B (EC50 = 2.61 μM in a luciferase reporter assay) and a metabolite of D-tryptophan.1 It increases levels of intracellular calcium and decreases forskolin-stimulated production of cAMP in CHO cells expressing human HCA3/GPR109B when used at concentrations of 10 and 100, or 1,000 μM, respectively. D-Kynurenine (10 μM) increases expression of vimentin and decreases expression of E-cadherin in 95D lung cancer cells.2 It has been used as a substrate in fluorometric assays for D-amino acid oxidase activity.3,4

|1. Irukayama-Tomobe, Y., Tanaka, H., Yokomizo, T., et al. Aromatic D-amino acids act as chemoattractant factors for human leukocytes through a G protein-coupled receptor, GPR109B. Proc. Natl. Acad. Sci. USA 106(10), 3930-3934 (2009).|2. Duan, Z., Li, Y., and Li, L. Promoting epithelial-to-mesenchymal transition by D-kynurenine via activating aryl hydrocarbon receptor. Mol. Cell. Biochem. 448(1-2), 165-173 (2018).|3. Kozaki, A., Iwasa, S., Hosoda, S., et al. Fluorimetric assay for D-amino acid oxidase activity in rat brain homogenate by using D-kynurenine as a substrate. Biosci. Trends 6(5), 241-247 (2012).|4. Song, Z., Ogaya, T., Ishii, K., et al. Utilization of kynurenic acid produced from D-kynurenine in an in vitro assay of D-amino acid oxidase activity. J. Health Sci. 56(3), 341-346 (2010).