Density Functional Theory Insights into the Role of the Methionine鈥揟yrosine鈥揟ryptophan Adduct Radical in the KatG Catalase Reaction: O2 Release from the Oxyheme Intermediate
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- 作者：Bonnie I. Kruft ; Richard S. Magliozzo ; Andrzej A. Jarz臋cki
- 刊名：Journal of Physical Chemistry A
- 出版年：2015
- 出版时间：July 2, 2015
- 年：2015
- 卷：119
- 期：26
- 页码：6850-6866
- 全文大小：680K
- ISSN：1520-5215
文摘
Density functional theory was employed for a comprehensive study that provided electronic and structural insights into the KatG catalase reaction that involves oxyheme. The catalytic role of a unique amino acid cofactor Met-Tyr-Trp (MYW) in its radical form found in KatG was thereby elucidated. It was established that the MYW-radical is flexible such that a 鈥渉inge-like opening鈥?rotation of the Trp-107 ring with respect to the Tyr-229 ring along their covalent C鈥揅 bond is an inherent feature of its catalytic properties. Also, an H-bond between the Tyr-229 and the mobile side chain of Arg-418 further enables the catalytic events. The opening process breaks an H-bond between the N鈥揌 of Trp-107 and the inner oxygen of the Fe鈥揙<sub>2sub> (oxyheme) complex present in the closed conformation of the MYW-radical. This motion lowers the spin-crossing energy barrier between the ground state and the catalytically active high-spin states and enables electron transfer from the oxyheme group to the MYW-radical. The release of molecular oxygen is thereby catalyzed and leaves ferric-heme poised for another catalytic cycle. The energy barrier for the oxyheme state to complete the catalytic event, when assisted by the radical opening process, is thereby reduced and estimated to be 5.6 kcal/mol.