Catalyzes the oxidative ring opening of 3-hydroxyanthranilate to 2-amino-3-carboxymuconate semialdehyde, which spontaneously cyclizes to quinolinate. 3-hydroxyanthranilate + O2 = (2Z,4Z)-2-amino-3-carboxymuconate 6-semialdehyde Cofactor biosynthesis; NAD(+) biosynthesis; quinolinate from L-kynurenine: step 3/3. Monomer. No visible phenotype. Mice were born at the expected Mendelian ratio and are normal. They however show very high levels of 3-hydroxyanthranilate compared to wild-type mice. Belongs to the 3-HAO family.