期刊
JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY
卷 21, 期 5-6, 页码 575-588出版社
SPRINGER
DOI: 10.1007/s00775-016-1372-9
关键词
Binuclear non-heme iron enzymes; O-2 activation; Variable-temperature; variable-field magnetic circular dichroism; Frontier molecular orbitals; Peroxide activation
资金
- National Science Foundation [MCB1404866]
- National Institutes of Health [GM040392]
- C1 Gas Refinery Program through National Research Foundation of Korea [2015M3D3A1A01064889]
- Korea Institute of Science and Technology Information [KSC-2015-C1-030]
- Div Of Molecular and Cellular Bioscience
- Direct For Biological Sciences [1404866] Funding Source: National Science Foundation
Binuclear non-heme iron enzymes activate O-2 to perform diverse chemistries. Three different structural mechanisms of O-2 binding to a coupled binuclear iron site have been identified utilizing variable-temperature, variable-field magnetic circular dichroism spectroscopy (VTVH MCD). For the mu-OH-bridged Fe(II)(2) site in hemerythrin, O-2 binds terminally to a five-coordinate Fe(II) center as hydroperoxide with the proton deriving from the mu-OH bridge and the second electron transferring through the resulting mu-oxo superexchange pathway from the second coordinatively saturated Fe(II) center in a proton-coupled electron transfer process. For carboxylate-only-bridged Fe(II)(2) sites, O-2 binding as a bridged peroxide requires both Fe(II) centers to be coordinatively unsaturated and has good frontier orbital overlap with the two orthogonal O-2 pi* orbitals to form peroxo-bridged Fe(III)(2) intermediates. Alternatively, carboxylate-only-bridged Fe(II)(2) sites with only a single open coordination position on an Fe(II) enable the one-electron formation of Fe(III)-O-2 (-) or Fe(III)-NO- species. Finally, for the peroxo-bridged Fe(III)(2) intermediates, further activation is necessary for their reactivities in one-electron reduction and electrophilic aromatic substitution, and a strategy consistent with existing spectral data is discussed.
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