Kynurenine aminotransferases (KATs) are pyridoxal-5'-phosphate-dependent enzymes that catalyze the conversion of L-kynurenine into kynurenic acid, a neuroactive metabolite whose unbalancing is associated with a number of brain disorders. Biochemical and structural investigations revealed that L-kynurenine (L-KYN) recognition by hKAT II is achieved by exploiting structural features that are peculiar of this isoform, thus offering the possibility to select/design inhibitor molecules specifically targeting hKAT II to be used as modulators of kynurenic acid synthesis in the CNS. hKAT II is one of the aminotransferases involved in the pyridoxal 5'-phosphate (PLP)-dependent irreversible transamination of L-kynurenine (L-KYN) to kynurenic acid (KYNA) in the central nervous system. When assayed in vitro the protein also displays beta-elimination activity.