Mechanism of the salicylate hydroxylase reaction.

1. A stable ternary complex of salicylate hydroxylase apoenzyme, flavin adenine dinucleotide, and salicylate was detected by a change of the absorption spectrum and by titration of the holoenzyme with salicylate. 2. The complex was enzymatically active, since the stoichiometric formation of the product, catechol, was observed upon introduction of air into a solution of reduced form of the complex. 3. On the basis of the results, the following scheme was postulated for the over-all reaction of salicylate hydroxylase.