The enzyme catalyses the ortho-hydroxylation of simple phenols into the corresponding catechols. It accepts 4-methylphenol, 4-chlorophenol, and 4-fluorophenol [1] as well as 4-nitrophenol, 3-nitrophenol, and resorcinol [3]. The enzyme is part of a two-component system that also includes an NADH-dependent flavin reductase. It is strictly dependent on FADH2 and does not accept FMNH2 [1,3]. cf. EC 1.14.13.7, phenol 2-monooxygenase (NADPH).