title: Hydrogen Abstraction of Camphor Catalyzed by Cytochrome P450cam: A QM/MM Study.
abstract: A combined quantum mechanics and molecular mechanics (QM/MM, QM = UB3LYP-D3, MM = AMBER) method is used to study the hydrogen abstraction reaction in P450camcatalyzed hydroxylation of camphor in the quartet state. Compared to QM/MM calculations in the literature, this study uses larger basis sets for the most important atoms at the active site and QM/MM Hessian harmonic frequency calculations to determine the standard Gibbs free energy of activation and kinetic isotope effect. The QM/MM covalent boundary is treated with a capping hydrogen atom method, which is simple and robust. An energy barrier of 21.3 kcal/mol and a standard free energy of activation of 16.8 kcal/mol are obtained for this hydrogen abstraction reaction. These values are similar to those reported in the literature, suggesting that when a general protocol is followed, QM/MM results are reproducible. It is found that using a sufficiently large basis set is important to minimize basis set errors.
authors.affiliation: Department of Chemistry and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln , Lincoln, Nebraska 68588-0304, United States.
authors.forename: Rui
authors.initials: R
authors.lastname: Lai
authors.affiliation: Department of Chemistry and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln , Lincoln, Nebraska 68588-0304, United States.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
mesh_terms: D055162:Biocatalysis; D019475:Camphor 5-Monooxygenase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism*; D011789:Quantum Theory
chemical_list: D006859:Hydrogen; D019475:Camphor 5-Monooxygenase