Fig. 2
From: Uremic toxins mediate kidney diseases: the role of aryl hydrocarbon receptor
Metabolic pathway of tryptophan (Trp). Trp is mainly degraded through three known metabolic pathways that can be initiated by the host, plant or microbiota. These include the KYN pathway (90–95% of Trp), serotonin pathway (1–2% of Trp) and indolic pathway (4–6% of Trp). Several compounds, including indoxyl sulfate (IS), kynurenine (KYN), kynurenic acid (KYNA), and indole-3-acetic acid (IAA), are recognized as uremic toxins and are marked with blue boxes. The compound acting as AhR ligands is marked with an asterisk (*)