Aromatic-ring hydroxylase-like Bacterial aromatic-ring hydroxylases (flavoprotein monooxygenases) incorporate one hydroxyl group into substrates. In this reaction, two atoms of dioxygen are reduced to one hydroxyl group and one H₂O molecule by the concomitant oxidation of NAD(P)H. Flavoprotein hydroxylases that catalyze the monohydroxylation of the aromatic ring carry out two reactions on a single polypeptide chain; the oxidation of NAD(P)H to generate two reducing equivalents, and the hydroxylation of substrates [<cite idref="PUB00000123"/>].