The origin of the oxygen incorporated during the dehalogenation/hydroxylation of 4-chlorobenzoate by an Arthrobacter sp.

An Arthrobacter sp. has been shown to dehalogenate 4-chlorobenzoate yielding 4-hydroxybenzoate. Experiments with 18O indicate that, in the presence of cell-free extracts, the hydroxyl group which is substituted onto the aromatic nucleus during dehalogenation is derived from water and not from molecular oxygen. Dehalogenation therefore is not catalysed by a mixed-function oxidase; instead a novel aromatic hydroxylase is implicated in the reaction.