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Fe-O versus O-O bond cleavage in reactive iron peroxide intermediates of superoxide reductase.
MedLine Citation:
PMID:  23135387     Owner:  NLM     Status:  Publisher    
It is generally accepted that the catalytic cycles of superoxide reductases (SORs) and cytochromes P450 involve a ferric hydroperoxo intermediate at a mononuclear iron center with a coordination sphere consisting of four equatorial nitrogen ligands and one axial cysteine thiolate trans to the hydroperoxide. However, although SORs and P450s have similar intermediates, SORs selectively cleave the Fe-O bond and liberate peroxide, whereas P450s cleave the O-O bond to yield a high-valent iron center. This difference has attracted the interest of researchers, and is further explored here. Meta hybrid DFT (M06-2X) results for the reactivity of the putative peroxo/hydroperoxo reaction intermediates in the catalytic cycle of SORs were found to indicate a high-spin preference in all cases. An exploration of the energy profiles for Fe-O and O-O bond cleavage in all spin states in both ferric and ferrous models revealed that Fe-O bond cleavage always occurs more easily than O-O bond cleavage. While O-O bond cleavage appears to be thermodynamically and kinetically unfeasible in ferric hydrogen peroxide complexes, it could occur as a minor (significantly disfavored) side reaction in the interaction of ferrous SOR with hydrogen peroxide.
Amr Ali Ahmed Ali Attia; Daniela Cioloboc; Alexandru Lupan; Radu Silaghi-Dumitrescu
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-8
Journal Detail:
Title:  Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry     Volume:  -     ISSN:  1432-1327     ISO Abbreviation:  J. Biol. Inorg. Chem.     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9616326     Medline TA:  J Biol Inorg Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Department of Chemistry and Chemical Engineering, "Babes-Bolyai" University, 1 Mihail Kogălniceanu str, 400084, Cluj-Napoca, Romania.
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