Cryoreduction of the NO-adduct of taurine:alpha-ketoglutarate dioxygenase (TauD) yields an elusive {FeNO}(8) species.
Cryoreduction of the NO-adduct of taurine:alpha-ketoglutarate dioxygenase (TauD) yields an elusive {FeNO}(8) species.
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牛磺酸：α-酮戊二酸双加氧酶 (TauD) 的 NO 加合物的冷冻还原产生难以捉摸的 {FeNO}(8) 物种。
DOI：
10.1021/ja909715g
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发表时间：
2010
影响因子：
15
通讯作者：
Neese,Frank
中科院分区：
文献类型：
--
作者：
Ye,Shengfa;Price,JohnC;Barr,EricW;Green,MichaelT;BollingerJr,JMartin;Krebs,Carsten;Neese,Frank
Fe(II) 和 α-酮戊二酸 (αKG) 依赖性酶是一组功能和机制多样化的单核非血红素铁酶，可激活双氧以将 αKG 的脱羧（产生琥珀酸和 CO2）与其底物的脂肪族 C−H 键的氧化偶联。人们通过结合动力学、光谱和计算方法对它们的机制进行了详细研究。该酶家族的几个成员已捕获并表征了两种反应中间体。第一个中间体是 C−H 裂解 Fe(IV)−氧配合物，它对其衰变表现出很大的氘动力学同位素效应。第二种中间体是 Fe(II):产物复合物。预计在 Fe(IV)−oxo 中间体之前发生的反应中间体不会积累，因此无法通过实验进行表征。这些中间体之一是最初的 O2 加合物，它是由 Enemark 和 Feltham 引入的符号中的 {FeO2}8 物种。在这里，我们报告了牛磺酸稳定的NO加合物：αKG双加氧酶（TauD）（称为TauD−{FeNO}7）及其单电子还原形式TauD−{FeNO}8的光谱和计算研究。后者与所提出的 O2 加合物是等电子的，是通过 TauD−{FeNO}7 的低温 γ 辐照产生的。据我们所知，TauD−{FeNO}8 是第一个顺磁 {FeNO}8 配合物。实验和计算结果的详细分析表明TauD−{FeNO}8具有三重基态。这具有本文讨论的机械含义。三重态 {FeNO}8 物质的退火可能会产生同样难以捉摸的具有五重态基态的 {FeHNO}8 配合物。
The Fe(II)- and α-ketoglutarate (αKG)-dependent enzymes are a functionally and mechanistically diverse group of mononuclear nonheme-iron enzymes that activate dioxygen to couple the decarboxylation of αKG, which yields succinate and CO2, to the oxidation of an aliphatic C−H bond of their substrates. Their mechanisms have been studied in detail by a combination of kinetic, spectroscopic, and computational methods. Two reaction intermediates have been trapped and characterized for several members of this enzyme family. The first intermediate is the C−H-cleaving Fe(IV)−oxo complex, which exhibits a large deuterium kinetic isotope effect on its decay. The second intermediate is a Fe(II):product complex. Reaction intermediates proposed to occur before the Fe(IV)−oxo intermediate do not accumulate and therefore cannot be characterized experimentally. One of these intermediates is the initial O2adduct, which is a {FeO2}8species in the notation introduced by Enemark and Feltham. Here, we report spectroscopic and computational studies on the stable NO-adduct of taurine:αKG dioxygenase (TauD), termed TauD−{FeNO}7, and its one-electron reduced form, TauD−{FeNO}8. The latter is isoelectronic with the proposed O2adduct and was generated by low-temperature γ-irradiation of TauD−{FeNO}7. To our knowledge, TauD−{FeNO}8is the first paramagnetic {FeNO}8complex. The detailed analysis of experimental and computational results shows that TauD−{FeNO}8has a triplet ground state. This has mechanistic implications that are discussed in this Article. Annealing of the triplet {FeNO}8species presumably leads to an equally elusive {FeHNO}8complex with a quintet ground state.