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投稿者: Yuma Morimoto

太農大先生の新作

Article

Flavonolate Complexes of MII (M = Mn, Fe, Co, Ni, Cu, and Zn). Structural and Functional Models for the ES (Enzyme–Substrate) Complex of Quercetin 2,3-Dioxygenase

Ying-Ji Sun *†, Qian-Qian Huang †, Tetsuro Tano ‡, and Shinobu Itoh ‡
† School of Chemistry, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
‡ Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
Inorg. Chem., Article ASAP
DOI: 10.1021/ic400972k
Publication Date (Web): September 17, 2013
Copyright © 2013 American Chemical Society

Abstract

Abstract Image
A series of flavonolate complexes [MIIL(fla)] (M = Mn (1), Fe (2), Co (3), Ni (4), Cu (5), and Zn (6), LH: 2-{[bis(pyridin-2-ylmethyl)amino]methyl}benzoic acid, fla: flavonolate) have been synthesized as structural and functional models for the ES (enzyme–substrate) complexes of the active site of various MII-containing quercetin 2,3-dioxygenase (2,3-QD) and their structures, spectroscopic features, and redox properties, as well as the reactivity toward molecular oxygen, have been investigated. The metal centers of [FeIIL(fla)]·H2O (2), [CoIIL(fla)]·CH3OH (3), and [NiIIL(fla)] (4) exhibit a distorted octahedral geometry with two oxygen atoms of fla, one oxygen atom of the benzoate group of ligand L, and three nitrogen atoms of ligand L, in which oxygen atom of the carbonyl group of fla and one of the pyridine nitrogen atoms occupy the axial positions. The complexes [MIIL(fla)] exhibit relatively high reactivity in the oxidative ring-opening of the bound flavonolate at lower temperature, presumably due to the existing carboxylate group in the supporting ligand. Thus, our complexes act as good functional ES models of various metal(II)-containing 2,3-QD. In addition, complexes [FeIIL(fla)]·H2O (2), [CoIIL(fla)]·CH3OH (3), and [NiIIL(fla)] (4) are the first structurally characterized FeII-, CoII-, and NiII-flavonolate complexes, as an active site ES model of FeII-, CoII-, and NiII-containing 2,3-QD, respectively. The model complexes exhibit notably different reactivity in the order of Fe (2) > Cu (5) > Co (3) > Ni (4) > Zn (6) > Mn (1). The differences in the reactivity among them may be attributed to the redox potential of the coordinated flavonolate of the complexes, which are remarkably influenced by the Lewis acidity of the metal ion and its coordination environment. Our study is the first example of the metal ion effects on the enzyme-like dioxygenation reactivity, providing important insights into the metal ion effects on the enzymatic reactivity of various metal(II)-containing 2,3-QD.

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