Studies on an iron(iii)-peroxo porphyrin. Iron(III)-peroxo or iron(II)-superoxo?
We demonstrate that a one electron reduced product of the heme iron dioxygen adduct exists in solution not only as the commonly accepted iron(iii)-peroxo species, but coexists with its isomeric iron(ii)-superoxo form. This unusual reduced metal-superoxide adduct [M(ii)-O(2)(-)] is recently reported as a reactive intermediate in the case of non-heme extradiol dioxygenases and could also be generated by cryoreduction of a heme Fe(II)-O(2) adduct. The existence of iron(ii)-superoxo species in solution is consistent with IR, EPR, mass and Mössbauer spectra. The equilibrium between heme iron(iii)-peroxo and iron(ii)-superoxo forms is supported by density functional theory and explains our previous finding that upon release of coordinated (su)peroxide a corresponding iron(ii) complex remains. These results shed new light on the nature of heme iron(iii)-peroxo species that are key intermediates in the metalloenzyme-catalyzed dioxygen and hydrogen peroxide activation.
Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg, Egerlandstr. 1, 91058 Erlangen, Germany.
Katharina
K
Duerr
Julianna
J
Olah
Roman
R
Davydov
Michael
M
Kleimann
Jing
J
Li
Nina
N
Lang
Ralph
R
Puchta
Eike
E
Hübner
Thomas
T
Drewello
Jeremy N
JN
Harvey
Norbert
N
Jux
Ivana
I
Ivanović-Burmazović
D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000737:chemistry*; D013058:Mass Spectrometry; D010545:Peroxides / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
D010545:Peroxides; D011166:Porphyrins; D007501:Iron