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H and other transfers in enzymes and in solution: Theory and computations, a unified view. 2. Applications to experiment and computations

Marcus, R. A. (2007) H and other transfers in enzymes and in solution: Theory and computations, a unified view. 2. Applications to experiment and computations. Journal of Physical Chemistry B, 111 (24). pp. 6643-6654. ISSN 1520-6106. doi:10.1021/jp071589s. https://resolver.caltech.edu/CaltechAUTHORS:20150317-104923432

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Abstract

Equations obtained in part I for the free-energy barrier to one-step enzymatic reactions between bound reactants are discussed. The rate is expressed in terms of λ_o (protein reorganization energy), ΔG° (standard free energy of reaction of the H-transfer step), bond breaking/bond forming term, w (work terms), and H-transmission property. Two alternative approximations for the coupling of the bond breaking/bond forming and protein are distinguished experimentally in favorable cases by the ΔG° where the maximum deuterium kinetic isotope effect occurs. Plots of log rate versus ΔG° and properties such as ΔS* and ΔS° are discussed. The weak or zero T-dependence of the kinetic isotope effect for wild-type enzymes operating under physiological conditions is interpreted in terms of vanishing (or isotopically insensitive) w plus transfer from the lowest H-state. Static and dynamic protein flexibility is discussed. While the many correlations accessible for electron transfers are not available for H-transfers in enzymes, a combination of experiment, computation, and analytical approaches can assist in evaluating the utility of the present equations and in suggesting further experiments and computations. A protein reorganization energy λ_o is obtained in the literature from the extended valence bond formalism where diabatic electronic states are used. A method is suggested for extracting it when instead a bond distance difference coordinate is used. The results may provide a bridge between the two approaches.


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http://dx.doi.org/10.1021/jp071589s DOIArticle
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ORCID:
AuthorORCID
Marcus, R. A.0000-0001-6547-1469
Additional Information:© 2007 American Chemical Society. Received: February 26, 2007; In Final Form: March 30, 2007. Published on Web May 12, 2007. I am pleased to acknowledge the support of this research by the National Science Foundation and the Office of Naval Research. I would like also to acknowledge the very helpful correspondence and suggestions from colleagues in the field: Jiali Gao, Sharon Hammes-Schiffer, Judith Klinman, Amnon Kohen, Don Truhlar, Arieh Warshel and Prof. Maria Michel-Beyerle and Dr. Yousung Jung. It is a particular pleasure to dedicate this article to Norman Sutin, who pioneered much that developed in the field of electron-transfer reactions, the work serving as a prelude to the present analysis.
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Office of Naval Research (ONR)UNSPECIFIED
Issue or Number:24
DOI:10.1021/jp071589s
Record Number:CaltechAUTHORS:20150317-104923432
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150317-104923432
Official Citation:H and Other Transfers in Enzymes and in Solution:  Theory and Computations, a Unified View. 2. Applications to Experiment and Computations R. A. Marcus The Journal of Physical Chemistry B 2007 111 (24), 6643-6654 DOI: 10.1021/jp071589s
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55851
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Mar 2015 18:00
Last Modified:10 Nov 2021 20:51

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