3-hydroxyanthranilate 3,4-dioxygenase is an enzyme encoded by the HAAO gene that catalyzes the chemical reaction 3-hydroxyanthranilate + O2 ⇌ {\displaystyle \rightleftharpoons } 2-amino-3-carboxymuconate semialdehydeThus, the two substrates of this enzyme are 3-hydroxyanthranilate and O2, whereas its product is 2-amino-3-carboxymuconate semialdehyde. Wikipedia