In enzymology, an aryl-aldehyde oxidase is an enzyme that catalyzes the chemical reaction an aromatic aldehyde + O2 + H2O ⇌ {\displaystyle \rightleftharpoons } an aromatic carboxylic acid + H2O2The 3 substrates of this enzyme are aromatic aldehyde, O2, and H2O, whereas its two products are aromatic carboxylic acid and H2O2. Wikipedia