This entry describes kynureninase, it is a pyridoxal-5'-phosphate (PLP)-dependent enzyme that catalyzes the hydrolytic cleavage of L-kynurenine to anthranilic acid and L-alanine. Kynurinine is a Trp breakdown product and a precursor for NAD. This reaction is a key step in the catabolism of L-tryptophan by Pseudomonas fluorescens and some other bacteria (1). In fungi and vertebrates, kynurenine is first hydroxylated to 3-hydroxykynurenine, which is the preferred substrate of kynureninase in those organisms, resulting in 3-hydroxyanthranilate and L-alanine.

Sequence alignment with other PLP-dependent enzymes indicated that kynureninase is in subgroup IVa of the aminotransferases, along with nifS, CsdB, and serine-pyruvate aminotransferase, which suggests that kynureninase has an aminotransferase fold [PMID:14756555].