FIGURE 1:

Tryptophan catabolism via the KP. Metabolites measured by LC-MS are depicted in the blue ovals. Rate-limiting enzymes of the KP are depicted in the red rectangles and include tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO). Other downstream enzymes of the KP are depicted in the dark gray rectangles and include kynureninase (Kyn), kynurenine aminotransferase (KAT), kynurenine monooxygenase (KMO) and 3-hydroxy anthranilic acid dioxygenase (3-HAA dioxygenase). Indole derivatives are depicted in the pink ovals and intermediates of the serotonin pathway, including 5-hydroxy tryptamine (5-HT), are depicted in the green ovals.