The enzyme urate oxidase (UO), or uricase or factor-independent urate hydroxylase, absent in humans, catalyzes the oxidation of uric acid to 5-hydroxyisourate: Uric acid + O2 + H2O →
5-hydroxyisourate + H2O2 → allantoin + CO2 http://www.creative-enzymes.com/product/Native-Candida-Sp-Uricase_771.html