A long-lived, substrate-hydroxylating peroxodiiron(III/III) intermediate in the amine oxygenase, AurF, from Streptomyces thioluteus.

The amine oxygenase AurF from Streptomyces thioluteus catalyzes the six-electron oxidation of p-aminobenzoate (pABA) to p-nitrobenzoate (pNBA). In this work, we have studied the reaction of its reduced Fe2(II/II) cofactor with O2, which results in generation of a peroxo-Fe2(III/III) intermediate. In the absence of substrate, this intermediate is unusually stable (t1/2 = 7 min at 20 °C), allowing for its accumulation to almost stoichiometric amounts. Its decay is accelerated ∼105-fold by the substrate, pABA, implying that it is the complex that effects the two-electron oxidation of the amine to the hydroxylamine. The nearly quantitative conversion of pABA to pNBA by solutions containing an excess of the intermediate suggests that it may also be competent for the two subsequent two-electron oxidations leading to the product.