title: Unique structural and electronic features of perferryl-oxo oxidant in Cytochrome P450.
abstract: We have performed hybrid density functional theory (DFT) calculations on the geometric and electronic structures of low-lying doublet and quartet ferryl-oxo [Fe(IV)═O] oxidants and a doublet perferryl-oxo [Fe(V)═O] oxidant in Cytochrome P450. Fully optimized structures of compound I models have been determined, and the proper symmetry of wave functions has been restored by the spin-projection technique. The results show that the perferryl-oxo species is relatively low lying, as compared with the excited state of the ferryl-oxo species, if the iron-oxo bond is properly described as the mixing of several appropriate excited electronic configurations to minimize electron repulsion. This means that the perferryl-oxo species is virtually in a mixed-valent resonance state, ↑Fe(V)═O ↔ ↑Fe(IV)•↑-↓•O, containing a highly reactive pπ atomic oxygen radical. The anionic thiolate ligand acts as a Lewis σ base and functions to achieve the stability of the perferryl-oxo complex and to activate the oxo ligand trans to it by asymmetric bond distortion along the O-Fe-S axis by lengthening the Fe-O bond and shortening the Fe-S bond, prior to the hydrogen-atom abstraction from the substrate.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. isobe@chem.sci.osaka-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Isobe
authors.forename: Syusuke
authors.initials: S
authors.lastname: Yamanaka
authors.forename: Mitsutaka
authors.initials: M
authors.lastname: Okumura
authors.forename: Kizashi
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: Jiro
authors.initials: J
authors.lastname: Shimada
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry*; D004583:Electrons; D007501:Iron / Q000737:chemistry*; D008968:Molecular Conformation
chemical_list: C066318:perferryl iron; D003577:Cytochrome P-450 Enzyme System; D007501:Iron