Research Article

The Genetic Link between Parkinson’s Disease and the Kynurenine Pathway Is Still Missing

Figure 1

Tryptophan metabolism. (I) Serotonin pathway: 1: tryptophan hydroxylase, 2: L-aromatic amino acid decarboxylase, and 3: serotonin-N-acetyltransferase and hydroxyindole-O-methyltransferase; (II) kynurenine pathway: 1: tryptophan dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO), 2: formamidase, 3: kynurenine aminotransferases (KATs), 4: kynurenine 3-monooxygenase (KMO), 5: kynureninase, 6: kynureninase, 7: 3-hydroxyanthranilic acid oxygenase, and 8: quinolinic acid phosphoribosyltransferase.