Cytochrome P450 aromatic O-demethylase is a bacterial enzyme that catalyzes the demethylation of lignin and various lignols.

The net reaction follows the following stoichiometry, illustrated with a generic methoxy arene:[1] The enzyme is notable for its promiscuity, affecting the O-demethylation of a range of substrates, including lignin.

GcoA process the substrate while GcoB provides the electrons to support the mixed function oxidase.

GcoA positions the aromatic ring within the hydrophobic active site cavity where the heme is located.

The surface of GcoB has an acidic patch that must interact with the matching basic region in GcoA.