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Improved free energy profile for reduction of NO in cytochrome c dependent nitric oxide reductase (cNOR)
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
2016 (Engelska)Ingår i: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 37, nr 19, s. 1810-1818Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Quantum chemical calculations play an essential role in the elucidation of reaction mechanisms for redox-active metalloenzymes. For example, the cleavage and the formation of covalent bonds can usually not be described only on the basis of experimental information, but can be followed by the calculations. Conversely, there are properties, like reduction potentials, which cannot be accurately calculated. Therefore, computational and experimental data has to be carefully combined to obtain reliable descriptions of entire catalytic cycles involving electron and proton uptake from donors outside the enzyme. Such a procedure is illustrated here, for the reduction of nitric oxide (NO) to nitrous oxide and water in the membrane enzyme, cytochrome c dependent nitric oxide reductase (cNOR). A surprising experimental observation is that this reaction is nonelectrogenic, which means that no energy is conserved. On the basis of hybrid density functional calculations a free energy profile for the entire catalytic cycle is obtained, which agrees much better with experimental information on the active site reduction potentials than previous ones. Most importantly the energy profile shows that the reduction steps are endergonic and that the entire process is rate-limited by high proton uptake barriers during the reduction steps. This result implies that, if the reaction were electrogenic, it would become too slow when the gradient is present across the membrane. This explains why this enzyme does not conserve any of the free energy released.

Ort, förlag, år, upplaga, sidor
2016. Vol. 37, nr 19, s. 1810-1818
Nyckelord [en]
density functional theory, catalytic reaction mechanisms, reduction potentials, free energy profiles, redox-active metalloenzymes
Nationell ämneskategori
Organisk kemi
Identifikatorer
URN: urn:nbn:se:su:diva-132939DOI: 10.1002/jcc.24396ISI: 000379161900006PubMedID: 27130561OAI: oai:DiVA.org:su-132939DiVA, id: diva2:957191
Tillgänglig från: 2016-09-01 Skapad: 2016-08-26 Senast uppdaterad: 2019-01-14Bibliografiskt granskad

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Blomberg, Margareta R. A.Siegbahn, Per E. M.
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