2His-COO、3His及3His-COO等不同活性中心的单核非血红素亚铁酶活化分子氧的生物模拟及其结构和功能的相关性

Mononuclear non-heme-Fe(II) enzymes (MNHEs) activate molecular oxygen to catalyze an impressive variety of enzymatic reactions by the oxidative C-C bond cleavage of the substrates. The active sites of the typical MNHEs have a 2His-carboxylate (Glu/Asp) "facil traid", for example, 4-hydroxyphenylpyruvate dioxygenase (HPPD). Recently, some MNHEs having a Fe(II) centers atypically coordinated with 2His, 3His (β-diketone dioxygenase, Dke1)), 3His-COO (quercetin 2,3-dioxygenase, 2,3-QD and iron acireductone dioxygenase, Fe-ARD) and 4His were also found. The Dek1 (3His) shows some substrate promiscuity, it displays some activity for 4-hydroxyphenylpyruvate (HPP) (the native substrate of HPPD (2His-COO)) and maltol (the derivates of the substrate of 2,3-QD (3His-COO)). Although these MNHEs have some structural flexibility of the active site and substrate promiscuity, their catalytic roles as well as the structure-function relationship are not clear yet. In order to get insights into the catalytic roles and the structure-function relationship among 2His, 2His-COO, 3His, 3His-COO and 4His Fe(II) active site MNHEs, we will design and synthesize a series of Fe(II)-complexes supported by the 2N, 2N-COO, 3N, 3N-COO and 4N model ligands as structural and functional models for these MNHEs. Details of their structures, spectroscopic features, redox properties, reactivity toward their common substrate (HPP and maltol) and dioxygen as well as the structure-property-reactivity relationship will be investigated. This study will provide important insights into the role of dioxygen activation, the catalytic role of these MNHEs, and the structure-function relationship among them.

单核非血红素亚铁酶(MNHEs)可活化利用分子氧氧化断裂底物的C-C键来催化各种不同的反应。典型的MNHEs活性中心由2His-COO与Fe(II)面式配位，如α-丙酮酸双加氧酶(HPPD)。但最近也发现了具有2His、3His(β-二酮双加氧酶,Dke1)、3His-COO(栎精2,3-双加氧酶, 2,3-QD和含铁酸式还原酮双加氧酶, Fe-ARD)及4His活性中心的MNHEs。活性中心为3His的Dke1对2His-COO和3His-COO的酶的底物也有活性。虽然这些酶具有活性中心结构上的柔性和底物的多样性，但对它们的催化机理和结构与功能的相关性却知之甚少。本项目旨弄清这些酶的结构和功能的相关性，通过对精心设计的2N、2N-COO、3N、3N-COO及4N模型配体的Fe(II)模型配合物与其共同底物和分子氧的反应性的系统研究，在分子水平上阐明它们的催化反应机理和结构与功能的相关性。

单核非血红素亚铁酶(MNHEs)可活化利用分子氧氧化断裂底物的C-C键来催化各种不同的反应。典型的MNHEs活性中心由2His-COO与Fe(II)面式配位，如4-羟基-α-苯丙酮酸双加氧酶(HPPD)。但最近也发现了具有3His(β-二酮双加氧酶, Dke1)、3His-COO(栎精2,4-双加氧酶, 2,4-QD和含铁酸式还原酮双加氧酶, Fe-ARD)及4His活性中心的MNHEs。3His活性中心的Dke1对2His-COO和3His-COO活性中心酶的底物也有活性。虽然这些酶具有活性中心结构上的柔性和底物的多样性，但对其催化反应机理和活性中心结构与功能的相关性知之甚少。本项目旨在分子水平上阐明2His-COO、3His、3His-COO及4His不同活性中心MNHEs的催化反应机理和活性中心结构和功能的相关性为目的，设计、合成和表征了吡啶和咪唑系列2N-COO、3N、3N-COO及4N多吡啶苯胺/多吡啶胺基苯甲酸模型配体及其邻位苯甲酸羧基对位/间位或苯环对位引入不同取代基(R: OMe, Me, H, Br, NO2)的一系列模型配体LnR，这些酶的共同模型底物及其1个苯环对位引入不同取代基(OH/OMe, Me, H, Br, NO2)的一系列不对称模型底物SnR，以及相应的M(II) (Fe, Mn, Co, Ni, Cu, Zn)模型配合物，并系统研究了其结构、性质、与分子氧和底物的反应性及其催化反应机理、分子氧的活化机理以及活性中心结构-性质-功能的相关性，得到了一些重要的研究结果和结论。首次用ESR捕获到了[LCuI(fla")]活性中间体的信号，为该活性中间体的存在提供了直接的实验证据，对2,4-QD分子氧的活化机理这一存在争论的问题提供了佐证。该研究不仅为在分子水平上阐明这些酶的催化反应机理和活性中心结构与功能的相关性，而且为开发高效、高选择性、廉价绿色Bio-inspired人工酶、抗氧化剂、生物医药等方面提供依据。有关2His-COO、3His、3His-COO及4His不同活性中心MNHEs的结构和功能的相关性方面的研究尚未见报道。