Recombinant Human Kynureninase Protein, CF

Kynureninase is a pyridoxal-5 (-phosphate-dependent enzyme that catalyzes the hydrolytic cleavage of the amino acids L-kynurenine and L-3-hydroxykynurenine to give either anthranilic acid or 3-hydroxyanthranilic acid and alanine (1). The enzyme is a member of the “kynurenine pathway” enzymes, through which the majority of dietary tryptophan is degraded in the liver, and is involved in the de novo biosynthesis of NAD⁺ (2, 3). Kynurenine pathway genes are expressed in immune system cells such as macrophages and microglia. During inflammatory responses, the kynurenine pathway in these cells produces quinolinic acid (QA) and not NAD⁺. QA excites neurons via the activation of NMDA (N-methyl-D-aspartate) receptors resulting in neuronal damage. The tissue-damaging process has been demonstrated in AIDS-related dementia complex, Alzheimer’s, stroke, epilepsy, and Huntington’s disease. Because Kynureninase is one of the key enzymes of QA production, its inhibitors may be useful for the treatment of neurological disorders. The recombinant Kynureninase has been shown to possess specificity for 3-hydroxykynurenine over kynurenine (4, 5).