Fig. 1: Summary of the kynurenine pathway.

The kynurenine pathway is involved in the catabolism of tryptophan. The production of picolinic acid is considered an anti-inflammatory branch of the pathway, whist the production of quinolinic acid is considered pro-inflammatory due to its ability to activate immune cells and induce cell death. ACMSD acts at a branching point in this pathway that determines which of these products is created. 3-HAO 3-hydroxyanthranilate oxidase, ACMSD α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase, KAT kynurenine aminotransferase, KMO kynurenine-3-monooxygenase, KYUN kynureninase.