人亚硫酸盐氧化酶活性位点的高分辨率扩展X射线吸收精细结构：与密度泛函理论及X射线晶体学结果的比较
High-resolution EXAFS of the active site of human sulfite oxidase: comparison with density functional theory and X-ray crystallographic results.
作者信息
Harris Hugh H, George Graham N, Rajagopalan K V
机构信息
School of Chemistry, University of Sydney, New South Wales 2006, Australia.
出版信息
Inorg Chem. 2006 Jan 23;45(2):493-5. doi: 10.1021/ic0512274.
Much of our knowledge about molybdenum enzymes has originated from EXAFS spectroscopy. This technique provides excellent bond-length accuracy but has only limited bond-length resolution. We have used EXAFS spectroscopy with an extended data range in an attempt to improve bond-length resolution for the molybdenum enzyme sulfite oxidase. The Mo site of sulfite oxidase has two oxygen and three Mo-S ligands (two from cofactor dithiolene plus a cysteine). For the oxidized (Mo(VI)) enzyme, we find that the three Mo-S bond lengths are very similar (within 0.05 A) at 2.41 A, as are the Mo=O ligands at 1.72 A. Density functional theory shows that this is consistent with the proposed active-site structure. The reduced (Mo(IV)) enzyme shows two Mo-S bond lengths at 2.35 A and one at 2.41 A (assigned to cofactor dithiolene and cysteine, respectively, from DFT), together with one Mo=O at 1.72 A and one Mo-OH(2) at 2.30 A.
我们关于钼酶的许多知识都源自扩展X射线吸收精细结构（EXAFS）光谱学。这项技术能提供出色的键长精度，但键长分辨率有限。我们使用了具有扩展数据范围的EXAFS光谱学，试图提高钼酶亚硫酸盐氧化酶的键长分辨率。亚硫酸盐氧化酶的钼位点有两个氧配体和三个钼-硫配体（两个来自辅因子二硫烯加上一个半胱氨酸）。对于氧化态（Mo(VI)）的酶，我们发现三个钼-硫键长在2.41 Å时非常相似（相差在0.05 Å以内），钼=氧配体在1.72 Å时也是如此。密度泛函理论表明这与所提出的活性位点结构一致。还原态（Mo(IV)）的酶显示出两个钼-硫键长为2.35 Å，一个为2.41 Å（根据密度泛函理论分别归属于辅因子二硫烯和半胱氨酸），同时还有一个钼=氧键长为1.72 Å和一个钼-OH₂键长为2.30 Å。
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