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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Mechanism of O-2 Activation by alpha-Ketoglutarate Dependent Oxygenases Revisited. A Quantum Chemical Study
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Mechanism of O-2 Activation by alpha-Ketoglutarate Dependent Oxygenases Revisited. A Quantum Chemical Study

机译：再次探讨由α-酮戊二酸依赖性加氧酶激活O-2的机制。量子化学研究

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摘要

Four mechanisms previously proposed for dioxygen activation catalyzed by alpha-keto acid dependent oxygenases (alpha-ICAO) were studied with dispersion-corrected DFT methods employing B3LYP and TPSSh functionals in combination with triple-zeta basis set (cc-pVTZ). The aim of this study was to revisit mechanisms suggested in the past decade and resolve remaining issues related to dioxygen activation. Mechanism A, which runs on the quintet potential energy surface (PES) and includes formation of an Fe(III)-superoxide radical anion complex, subsequent oxidative decarboxylation, and O-O bond cleavage, was found. to be most likely. However, mechanism B taking place on the septet PES involves a rate limiting barrier comparable to the one found for mechanism A, and thus it cannot be excluded, though two other mechanisms (C and D) were ruled out. Mechanism C is a minor variation of mechanism A, whereas mechanism D proceeds through formation of a triplet Fe(IV)-alkyl peroxo bridged intermediate. The study covered also full optimization of relevant minimum energy crossing points (MECPs). The relative energy of critical intermediates was also studied with the CCSD(T) method in order to benchmark TPSSh and B3LYP functionals with respect to their credibility in predicting relative energies of septet and triplet spin states of the ternary enzyme Fe-alpha-keto glutarate (alpha-KG)-O-2 complex.
机译：使用分散校正的DFT方法，结合B3LYP和TPSSh功能以及三重Zeta基集（cc-pVTZ），研究了先前提出的由α-酮酸依赖性加氧酶（alpha-ICAO）催化的双氧活化的四种机理。这项研究的目的是重新审视过去十年中提出的机制，并解决与双氧激活有关的其余问题。发现了在五重态势能表面（PES）上运行的机理A，该机理包括形成Fe（III）-超氧化物自由基阴离子络合物，随后的氧化脱羧和O-O键断裂。最有可能。但是，发生在七峰PES上的机制B涉及一个与机制A所发现的机制相当的限速屏障，因此尽管排除了其他两种机制（C和D），也不能将其排除在外。机理C是机理A的微小变化，而机理D通过三重态Fe（IV）-烷基过氧桥接中间体形成。该研究还涵盖了相关最小能量穿越点（MECP）的全面优化。还使用CCSD（T）方法研究了关键中间体的相对能量，以便就TPSSh和B3LYP官能团在预测三元酶戊二酸Fe-α-酮戊二酸的九肽和三重态自旋态的相对能量方面的可信度进行基准测试（ α-KG）-O-2复合物。

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