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          Institute: MPI für Biochemie     Collection: Structure Research (R. Huber)     Display Documents

ID: 41732.0, MPI für Biochemie / Structure Research (R. Huber)
Mechanism of the six-electron reduction of nitrite to ammonia by cytochrome c nitrite reductase
Authors:Einsle, O.; Messerschmidt, A.; Huber, R.; Kroneck, P. M. H.; Neese, F.
Date of Publication (YYYY-MM-DD):2002-10-02
Title of Journal:Journal of the American Chemical Society
Journal Abbrev.:J. Am. Chem. Soc.
Issue / Number:39
Start Page:11737
End Page:11745
Review Status:Peer-review
Audience:Not Specified
Abstract / Description:Cytochrome c nitrite reductase catalyzes the six-electron reduction of nitrite to ammonia without the release of potential reaction intermediates, such as NO or hydroxylamine. On the basis of the crystallographic observation of reaction intermediates and of density functional calculations, we present a working hypothesis for the reaction mechanism of this multiheme enzyme which carries a novel lysine-coordinated heme group (Fe-Lys). It is proposed that nitrite reduction starts with a heterolytic cleavage of the N-O bond which is facilitated by a pronounced back-bonding interaction of nitrite coordinated through nitrogen to the reduced(Fe(II)) but not the oxidized (Fe(Ill)) active site iron. This step leads to the formation of an {FeNO}(6) species and a water molecule and is further facilitated by a hydrogen bonding network that induces an electronic asymmetry in the nitrite molecule that weakens one N-O bond and strengthens the other. Subsequently, two rapid one-electron reductions lead to an {FeNO}(8) form and, by protonation, to an Fe(II)-HNO adduct. Hereafter, hydroxylamine will be formed by a consecutive two-electron two-proton step which is dehydrated in the final two-electron reduction step to give ammonia and an additional water molecule. A single electron reduction of the active site closes the catalytic cycle.
Comment of the Author/Creator:Date: 2002, OCT 2
External Publication Status:published
Document Type:Article
Communicated by:N.N.
Affiliations:MPI für Biochemie/Structure Research (Huber)/Research Group A. Messerschmidt
External Affiliations:CALTECH, Howard Hughes Med Inst, Mail Code 147-75CH, Pasadena,; CA 91125 USA; Univ Konstanz, Math Nat Wissensch Sekt, Fachbereich Biol, D-78457 Constance, Germany
Identifiers:ISI:000178317100044 [ID No:1]
ISSN:0002-7863 [ID No:2]
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