Kynurenine

 L -Kynurenine is a metabolite of the amino acid L -tryptophan used in the production of niacin. It has been associated with tics.

Kynureninase catabolizes the conversion of kynurenine into anthranilic acid while kynurenine-oxoglutarate transaminase catabolizes its conversion into kynurenic acid. Kynurenine 3-hydroxylase converts kynurenine to 3-hydroxykynurenine.