Catalyzes the cleavage of L-kynurenine (L-Kyn) and L-3-hydroxykynurenine (L-3OHKyn) into anthranilic acid (AA) and 3-hydroxyanthranilic acid (3-OHAA), respectively. Has a preference for the L-3-hydroxy form. Also has cysteine-conjugate-beta-lyase activity.
Expressed in all tissues tested (heart, brain placenta, lung, liver, skeletal muscle, kidney and pancreas). Highest levels found in placenta, liver and lung. Expressed in all brain regions.
Amino-acid degradation; L-kynurenine degradation; L-alanine and anthranilate from L-kynurenine: step 1/1. Cofactor biosynthesis; NAD(+) biosynthesis; quinolinate from L-kynurenine: step 2/3.
Note=Xanthurenic aciduria manifesting as massive urinary excretion of large amounts of kynurenine, 3-hydroxykynurenine and xanthurenic acid has been observed in an individual carrying a homozygous missense change in KYNU (PubMed:17334708). The urinary pattern in the patient suggests kynureninase deficiency and a block in the conversion of kynurenine and 3-hydroxykynurenine to anthranilate and 3-hydroxyanthranilate, respectively.