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Oxygen-18 Kinetic Isotope Effects of Nonheme Iron Enzymes HEPD and MPnS Support Iron(III) Superoxide as the Hydrogen Abstraction Species.

  • Author(s): Zhu, Hui
  • Peck, Spencer C
  • Bonnot, Florence
  • van der Donk, Wilfred A
  • Klinman, Judith P
  • et al.

Published Web Location

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4970508/
No data is associated with this publication.
Abstract

Nonheme iron oxygenases that carry out four-electron oxidations of substrate have been proposed to employ iron(III) superoxide species to initiate this reaction [Paria, S.; Que, L.; Paine, T. K. Angew. Chem. Int. Ed. 2011, 50, 11129]. Here we report experimental evidence in support of this proposal. (18)O KIEs were measured for two recently discovered mononuclear nonheme iron oxygenases: hydroxyethylphosphonate dioxygenase (HEPD) and methylphosphonate synthase (MPnS). Competitive (18)O KIEs measured with deuterated substrates are larger than those measured with unlabeled substrates, which indicates that C-H cleavage must occur before an irreversible reductive step at molecular oxygen. A similar observation was previously used to implicate copper(II) superoxide in the H-abstraction reactions catalyzed by dopamine β-monooxygenase [Tian, G. C.; Klinman, J. P. J. Am. Chem. Soc. 1993, 115, 8891] and peptidylglycine α-hydroxylating monooxygenase [Francisco, W. A.; Blackburn, N. J.; Klinman, J. P. Biochemistry 2003, 42, 1813].

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