The molecule is tha amino acid zwitterion formed from 5-hydroxy-L-kynurenine by transfer of a proton from the carboxy to the amino group; principal microspecies at pH 7.3. It is a tautomer of a 5-hydroxy-L-kynurenine.
(2S)-4-(2-amino-5-hydroxyphenyl)-2-azaniumyl-4-oxobutanoate