Nucleoside oxidase (EC 1.1.3.28) is an enzyme with systematic name nucleoside:oxygen 5'-oxidoreductase.^[1][2] This enzyme catalyses the following chemical reaction

inosine + O₂ ${\displaystyle \rightleftharpoons }$ 9-riburonosylhypoxanthine + H₂O

(1a) 2 inosine + O₂ ${\displaystyle \rightleftharpoons }$ 2 5'-dehydroinosine + 2 H₂O

(1b) 2 5'-dehydroinosine + O₂ ${\displaystyle \rightleftharpoons }$ 2 9-riburonosylhypoxanthine

This enzyme could use other purine and pyrimidine nucleosides (as well as 2'-deoxynucleosides) as substrates.