Toluene/o-xylene monooxygenase (ToMO) is a non-heme diiron protein that activates O₂ for subsequent arene oxidation. ToMO utilizes four protein components, a catalytic hydroxylase, a regulatory protein, a Rieske protein, and a reductase. O₂ activation and substrate hydroxylation in the presence of all four protein components is examined. These studies demonstrate the importance of native reductants by revealing reactivity unobserved when dithionite and mediators are used as the reductant. This reactivity is compared with that of other O₂-activating diiron enzymes.United States. National Institutes of Health (GM032134)United States. National Institutes of Health (T32GM008334
