Kynurenine pathway

The kynurenine pathway or tryptophan kynurenine pathway is the primary route for metabolizing the essential amino acid tryptophan in humans and other mammals https://europepmc.org/articles/PMC4482796/ If the kynurenine pathway becomes dysregulated or overactive, it can activate the immune system and result in a build-up of potentially neurotoxic compounds in the body.

Function
The kynurenine pathway

ME/CFS
The metabolic trap hypothesis suggests that a metabolic problem exists in one or more areas of a person with ME/CFS, with a defect in the IDO2 enzyme of the tryptophan kynurenine pathway being identified as a possible metabolic trap.