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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >DFT Study on the Catalytic Reactivity of a Functional Model Complex for Intradiol-Cleaving Dioxygenases
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DFT Study on the Catalytic Reactivity of a Functional Model Complex for Intradiol-Cleaving Dioxygenases

机译：DFT研究功能模型复合物对二醇内裂解双加氧酶的催化反应性

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摘要

The enzymatic ring cleavage of catechol derivatives is catalyzed by two groups of dioxygenases: extradiol-and intradiol-cleaving dioxygenases. Although having different oxidation state of their nonheme iron sites and different ligand coordinations, both groups of enzymes involve a common peroxy intermediate in their catalytic cycles. The factors that lead to either extradiol cleavage resulting in 2-hydroxymuconaldehyde or intradiol cleavage resulting in muconic acid are not fully understood. Well-characterized model compounds that mimic the functionality of these enzymes offer a basis for direct comparison to theoretical results. In this study the mechanism of a biomimetic iron complex is investigated with density functional theory (DFT). This complex catalyzes the ring opening of catecholate with exclusive formation of the intradiol cleaved product. Several spin states are possible for the transition metal system, with the quartet state found to be of main importance during the reaction course. The mechanism investigated provides an explanation for the observed selectivity of the complex. First, a bridging peroxide is formed, which decomposes to an alkoxy radical by O-O homolysis. In contrast to the subsequent barrier-free intradiol C-C bond cleavage, the extradiol pathway proceeds via the formation of an epoxide, which requires an additional activation barrier.
机译：儿茶酚衍生物的酶促环裂解由两组双加氧酶催化：二醇外和二醇内裂解的双加氧酶。尽管它们的非血红素铁位点具有不同的氧化态和不同的配体配位，但是这两组酶在其催化循环中都包含一个共同的过氧中间体。导致2-羟基粘康醛的二醇外切割或导致粘康酸的二醇内切割的因素尚未完全理解。模仿这些酶功能的特征明确的模型化合物为直接与理论结果进行比较提供了基础。在这项研究中，用密度泛函理论（DFT）研究了仿生铁络合物的机理。该复合物催化儿茶酚酸酯的开环，而形成内二醇裂解产物。过渡金属体系可能有几种自旋态，在反应过程中四方态是最重要的。研究的机理为观察到的配合物的选择性提供了解释。首先，形成桥连的过氧化物，其通过O-O均解分解为烷氧基。与随后的无障碍的内部二醇内C-C键裂解相反，外部二醇途径通过环氧化物的形成进行，这需要附加的激活屏障。

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