ABSTRACT
The most extensively studied flavin-dependent monooxygenase is p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens. The internai flavin-dependent monooxygenases transform the substrate by hydroxylation followed by decarboxylation, i.e., oxidative decarboxylation. This chapter deals with monooxygenases containing only flavin as a prosthetic group. The flavoproteins in this class are conveniently divided into two categories: internai and external monooxygenases. The enzymatic monooxygenation reaction of an organic compound under physiological conditions requires activation of oxygen. The enzyme shows mixed-type inhibition in the presence of high concentrations of p-hydroxybenzoate or substrate analogs. The effect of the substrate on the conformation of the enzyme upon binding is best demonstrated by circular dichroism spectra. The conformation of free reduced enzyme must be similar to that of the oxidized ES complex, but dissimilar to that of free oxidized enzyme. The sterochemical reduction of the enzyme was studied using 8-hydroxy-8-demethyl-5-deaza-flavin adenine dinucleotide reconstituted enzyme.
