Purine N-Oxides

Xanthine oxidase (EC 1.2.3.2) has been shown to reduce the N-oxide function of several purine N-oxide derivatives. The reaction requires anaerobic conditions and electron donors such as xanthine, hypoxanthine, sodium dithionite, or DPNH. With no other electron donor present, the purine N-oxide can also serve as the electron donor if it has an oxidizable carbon atom. With sodium dithionite as the electron donor, a spectrometric procedure has been devised which permits measurement of the enzymatic reduction of N-oxides or other compounds by monitoring the disappearance of the dithionite absorption. The enzymatic synthesis of 8-hydroxyguanine 3-oxide is described.