| Proton-coupled electron transfer in soybean lipoxygenase: dynamical behavior and temperature dependence of kinetic isotope effects. | |
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MedLine Citation:
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PMID: 17199298 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The dynamical behavior and the temperature dependence of the kinetic isotope effects (KIEs) are examined for the proton-coupled electron transfer reaction catalyzed by the enzyme soybean lipoxygenase. The calculations are based on a vibronically nonadiabatic formulation that includes the quantum mechanical effects of the active electrons and the transferring proton, as well as the motions of all atoms in the complete solvated enzyme system. The rate constant is represented by the time integral of a probability flux correlation function that depends on the vibronic coupling and on time correlation functions of the energy gap and the proton donor-acceptor mode, which can be calculated from classical molecular dynamics simulations of the entire system. The dynamical behavior of the probability flux correlation function is dominated by the equilibrium protein and solvent motions and is not significantly influenced by the proton donor-acceptor motion. The magnitude of the overall rate is strongly influenced by the proton donor-acceptor frequency, the vibronic coupling, and the protein/solvent reorganization energy. The calculations reproduce the experimentally observed magnitude and temperature dependence of the KIE for the soybean lipoxygenase reaction without fitting any parameters directly to the experimental kinetic data. The temperature dependence of the KIE is determined predominantly by the proton donor-acceptor frequency and the distance dependence of the vibronic couplings for hydrogen and deuterium. The ratio of the overlaps of the hydrogen and deuterium vibrational wavefunctions strongly impacts the magnitude of the KIE but does not significantly influence its temperature dependence. For this enzyme reaction, the large magnitude of the KIE arises mainly from the dominance of tunneling between the ground vibronic states and the relatively large ratio of the overlaps between the corresponding hydrogen and deuterium vibrational wavefunctions. The weak temperature dependence of the KIE is due in part to the dominance of the local component of the proton donor-acceptor motion. |
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Authors:
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Elizabeth Hatcher; Alexander V Soudackov; Sharon Hammes-Schiffer |
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Publication Detail:
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Type: Journal Article; Research Support, N.I.H., Extramural; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Journal of the American Chemical Society Volume: 129 ISSN: 0002-7863 ISO Abbreviation: J. Am. Chem. Soc. Publication Date: 2007 Jan |
Date Detail:
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Created Date: 2007-01-03 Completed Date: 2007-04-18 Revised Date: 2007-12-03 |
Medline Journal Info:
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Nlm Unique ID: 7503056 Medline TA: J Am Chem Soc Country: United States |
Other Details:
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Languages: eng Pagination: 187-96 Citation Subset: IM |
Affiliation:
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Department of Chemistry, 104 Chemistry Building, Pennsylvania State University, University Park, Pennsylvania 16802, USA. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Electron Transport Entropy Isotopes / chemistry Kinetics Lipoxygenase / chemistry* Protons* Soybean Proteins / chemistry* Temperature |
| Grant Support | |
ID/Acronym/Agency:
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GM56207/GM/NIGMS NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Isotopes; 0/Protons; 0/Soybean Proteins; EC 1.13.11.12/Lipoxygenase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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