4-methoxybenzoate monooxygenase (O-demethylating) () is an enzyme that catalyzes a chemical reaction that removes the methyl group in p-anisic acid, giving a phenol, 4-hydroxybenzoic acid. It was characterised from Pseudomonas putida.
The methyl group is oxidised to formaldehyde. The enzyme is an oxidoreductase that uses molecular oxygen and an unknown electron acceptor. It is a flavoprotein that has flavin adenine dinucleotide as a cofactor. The systematic name of this enzyme class is 4-methoxybenzoate,hydrogen-donor:oxygen oxidoreductase (O-demethylating). Other names in common use include 4-methoxybenzoate 4-monooxygenase (O-demethylating), 4-methoxybenzoate O-demethylase, p-anisic O-demethylase, and piperonylate-4-O-demethylase.
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