Tryptophan is also metabolized by a separate pathway to kynurenine
by the enzyme, indoleamine 2,3-dioxygenase (IDO).
When you exercise, the levels of an enzyme called kynurenine
aminotransferase build up in your muscles.
Also, the fact that alterations have been observed in the kynurenine
pathway in tyrosine metabolism in parkinsonian fly, it can be concluded that kynurenine
pathway which is a metabolic pathway leading to the production of nicotinamide adenine dinucleotide (NAD +) from the degradation of the essential amino tryptophan acid, may be associated with Parkinson's disease.
Inflammation-associated depression: from serotonin to kynurenine
. Psychoneuroendocrinology 2011;36:426-36.
In a randomized, crossover feeding study including 11 obese nondiabetic participants, plasma concentrations of tryptophan, phenylalanine, and kynurenine
were increased after a high-fat meal with whey protein isolate (35).
Stroup et al., "Metabolomic changes demonstrate reduced bioavailability of tyrosine and altered metabolism of tryptophan via the kynurenine
pathway with ingestion of medical foods in phenylketonuria," Molecular Genetics and Metabolism, vol.
Kelley, "Inflammation-associated depression: from serotonin to kynurenine
," Psychoneuroendocrinology, vol.
Additionally, CTLA-4 induces the expression of the enzyme indoleamine 2,3-dioxygenase (IDO) by DCs, which catalyzes degradation of the essential amino acid tryptophan to kynurenine
, leading to effector T cell starvation .
Orhan et al., "Erratum:Skeletal muscle PGC-1a1 modulates kynurenine
metabolism and mediates resilience to stress-induced depression (Cell (2014) 159 (3345))," Cell, vol.
Indoleamine-2,3-dioxygenase, which catalyzes the oxidative breakdown of the essential amino acid tryptophan, via the kynurenine
pathway, is an inhibitor of T-cell proliferation that has been implicated in immune resistance in several cancers, including soft tissue sarcoma .
 reported that kynurenine
3-monooxygenase (KMO), an enzyme playing a critical role in Huntington's and Alzheimer's diseases, exhibits tumor-promoting effects towards HCC.
They also have immunomodulatory and immunosuppressive properties through the direct interaction between cells and secretion of prostaglandin E2 (PGE2), leukaemia-inhibiting factor (LIF), and kynurenine