3-Hydroxyanthranilate-3,4-dioxygenase, cupin domain
3-Hydroxyanthranilate-3,4-dioxygenase (HAO or 3HAO) is a non-heme iron-dependent extradiol dioxygenase that catalyzes the oxidative ring opening of 3-hydroxyanthranilate (3-HAA) in the final enzymatic step of the kynurenine biosynthetic pathway in which tryptophan is converted to quinolinate, an endogenous neurotoxin, making HAO a target for pharmacological downregulation. Quinolate is also the universal de novo precursor to the pyridine ring of nicotinamide adenine dinucleotide. The enzyme forms homodimers, with two metal binding sites per molecule. One of the bound metal ions occupies the proposed ferrous-coordinated active site, which is located in a conserved double-strand beta-helix domain. Proteins in this family belong to the cupin superfamily with a conserved "jelly roll-like" beta-barrel fold.
Jiyao W et al.(2023). "The conserved domain database in 2023.",