Fig. 1

Illustrated summary of the Kynurenine and Serotonergic pathways of tryptophan metabolism, enzymes highlighted in ovals. Potential loci of dysfunction discussed in this review are highlighted in pink. Abbreviations not mentioned in text: KAT- Kynurenine aminotransferase, KYNU - Kynureninase, KMO - Kynurenine 3-monooxygenase, ACMSD - aminocarboxymuconate-semialdehyde decarboxylase, QPRT - quinolate phosphoribosyl transferase. Figure adapted from Correia and Vale [86]. Figure created using BioRender [172]