Hypoxanthine as a Cofactor for the Enzymatic Oxidation of Sulfite

The oxidation of sulfite to sulfate by liver has been shown to be catalyzed by an enzyme system, of which some of the properties have been described (l-3). In continuation of these studies it was found that a partially purified enzyme preparation was inactivated by dialysis and reactivated by a thermostable factor from liver. This factor has been isolated and identified as hypoxanthine. EXPERIMENTAL