title: Four-electron oxidation of p-hydroxylaminobenzoate to p-nitrobenzoate by a peroxodiferric complex in AurF from Streptomyces thioluteus.
abstract: The nonheme di-iron oxygenase, AurF, converts p-aminobenzoate (Ar-NH(2), where Ar = 4-carboxyphenyl) to p-nitrobenzoate (Ar-NO(2)) in the biosynthesis of the antibiotic, aureothin, by Streptomyces thioluteus. It has been reported that this net six-electron oxidation proceeds in three consecutive, two-electron steps, through p-hydroxylaminobenzoate (Ar-NHOH) and p-nitrosobenzoate (Ar-NO) intermediates, with each step requiring one equivalent of O(2) and two exogenous reducing equivalents. We recently demonstrated that a peroxodiiron(III/III) complex (peroxo- -AurF) formed by addition of O(2) to the diiron(II/II) enzyme ( -AurF) effects the initial oxidation of Ar-NH(2), generating a mu-(oxo)diiron(III/III) form of the enzyme (mu-oxo- -AurF) and (presumably) Ar-NHOH. Here we show that peroxo- -AurF also oxidizes Ar-NHOH. Unexpectedly, this reaction proceeds through to the Ar-NO(2) final product, a four-electron oxidation, and produces -AurF, with which O(2) can combine to regenerate peroxo- -AurF. Thus, conversion of Ar-NHOH to Ar-NO(2) requires only a single equivalent of O(2) and (starting from -AurF or peroxo- -AurF) is fully catalytic in the absence of exogenous reducing equivalents, by contrast to the published stoichiometry. This novel type of four-electron N-oxidation is likely also to occur in the reaction sequences of nitro-installing di-iron amine oxygenases in the biosyntheses of other natural products.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, 16802, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.forename: Victoria Korneeva
authors.initials: VK
authors.lastname: Korboukh
authors.forename: Carsten
authors.initials: C
authors.lastname: Krebs
authors.forename: J Martin
authors.initials: JM
authors.lastname: Bollinger
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D019817:Benzoic Acid / Q000737:chemistry / Q000378:metabolism*; D002384:Catalysis; D004583:Electrons; D005290:Ferric Compounds / Q000378:metabolism*; D010084:Oxidation-Reduction; D015204:Spectroscopy, Mossbauer; D013302:Streptomyces / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005290:Ferric Compounds; D019817:Benzoic Acid
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