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. Author manuscript; available in PMC: 2020 Jul 9.
Published in final edited form as: Methods Enzymol. 2019 Jul 24;629:235–256. doi: 10.1016/bs.mie.2019.07.006

Fig. 1.

Fig. 1

The metabolic kynurenine (Kyn) conversion pathway. In addition to being used as building block for protein synthesis, the majority of dietary tryptophan (95%) is catabolized via the Trp→Kyn pathway (red arrows). Within the Kyn pathway, underlined metabolites can cross the blood brain barrier (BBB). IDO1 (and TDO) are highlighted in the black box. 3-HAO, 3-hydroxyanthranilate 3,4-dioxygenase; ACMSD, 2-amino-3-carboxymuconate semialdehyde carboxylase; KAT, kynurenine aminotransferase (I, II, III); KAT, kynurenine aminotransferase (I, II, III); KMO, kynurenine 3-monooxygenase; KYNU, kynureninase; QPRT, quinolinic-acid phosphoribosyl transferase.