Resonance Raman studies of the Iron(II)-α-keto acid chromophore in model and enzyme complexes
Resonance Raman studies of the Iron(II)-α-keto acid chromophore in model and enzyme complexes
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DOI：
10.1021/ja0041775
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发表时间：
2001-05-30
影响因子：
15
通讯作者：
Que, L
中科院分区：
文献类型：
--
作者：
Ho, RYN;Mehn, MP;Que, L
cl -酮酸通过酮基团和羧酸与铁（II）中心的双齿配位，在模型配合物和a-酮戊二酸依赖的双加氧酶中产生400至600 nm之间的金属到配体的电荷转移转变。Fe(II)TauD（α -KG）复合物（TauD =牛磺酸/ α -酮戊二酸双加氧酶，α -KG = α -酮戊二酸）的这些吸收带激发引起460和1686 cm（-1）处的两个共振拉曼特征，这两个特征都对O-18标记敏感。相应的模型配合物，六坐标[Fe(II)(6-Me-3-TPA)（α -酮酸）]（+）和五坐标[Fe(II)(Tp(Ph2))- （α -酮酸）]（6-Me-3-TPA = tris[（6-甲基-2-吡啶基）甲基]胺，Tp（Ph2) = hydrotris（3,5-二苯基吡唑-1-基）硼酸盐））的研究，导致这两个特征分别分配给Fe(II)（a-酮酸）螯合模式和v（C=O）酮羰基。此外，螯合模式对金属中心的配位数很敏感：第六配体与五坐标[Fe(II)(Tp(Ph2))（苯甲酰甲酸酯）]结合会引起9-20 cm（-1）的降移。因此，在添加底物牛磺酸后，观察到Fe(II)TauD（α -KG）的螯合模式上升了10 cm(-1)，这与六坐标金属中心向五坐标中心的转换有关。从x射线晶体学观察到克拉氨酸合酶的铁中心（Zhang， Z.：等）。Nat。结构。生物学报，2000,7。127-133)和MCD研究(Zhou， J.; et al.；j。化学。第1998,120,13539 -13540节)。这些研究为α -酮戊二酸依赖双加氧酶的氧激活机制的初始步骤提供了有用的见解。
The bidentate coordination of an CL-keto acid to an iron(II) center via the keto group and the carboxylate gives rise to metal-to-ligand charge-transfer transitions between 400 and 600 nm in model complexes and in a-ketoglutarate-dependent dioxygenases. Excitation into these absorption bands of the Fe(II)TauD(alpha -KG) complex (TauD = taurine/alpha -ketoglutarate dioxygenase, alpha -KG = alpha -ketoglutarate) elicits two resonance Raman features at 460 and 1686 cm(-1), both of which are sensitive to O-18 labeling. Corresponding studies of model complexes, the six-coordinate [Fe(II)(6-Me-3-TPA)(alpha -keto acid)](+) and the five-coordinate [Fe(II)(Tp(Ph2))- (alpha -keto acid)] (6-Me-3-TPA = tris[(6-methyl-2-pyridyl)methyl]amine, Tp(Ph2) = hydrotris(3,5-diphenylpyrazol-1-yl)borate), lead to the assignment of these two features to the Fe(II)(a-keto acid) chelate mode and the v(C=O) of the keto carbonyl group, respectively. Furthermore, the chelate mode is sensitive to the coordination number of the metal center: binding of a sixth ligand to the five-coordinate [Fe(II)(Tp(Ph2)) (benzoylformate)] elicits a 9-20 cm(-1) downshift. Thus, the 10 cm(-1) upshift of the chelate mode observed for Fe(II)TauD(alpha -KG) upon the addition of the substrate, taurine, is associated with the conversion of the six-coordinate metal center to a five-coordinate center. as observed for the iron center of clavaminate synthase from X-ray crystallography (Zhang, Z.: et al. Nat. Struct. Biol. 2000, 7. 127-133) and MCD studies (Zhou, J.; et al. J. Am. Chem. Sec. 1998, 120, 13539-13540). These studies provide useful insights into the initial steps of the oxygen activation mechanism of alpha -ketoglutarate-dependent dioxygenases.