A hyperactive cobalt-substituted extradiol-cleaving catechol dioxygenase.
A hyperactive cobalt-substituted extradiol-cleaving catechol dioxygenase.
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DOI：
10.1007/s00775-010-0732-0
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发表时间：
2011-02
影响因子：
3
通讯作者：
Que, Lawrence, Jr.
中科院分区：
文献类型：
--
作者：
Fielding, Andrew J.;Kovaleva, Elena G.;Farquhar, Erik R.;Lipscomb, John D.;Que, Lawrence, Jr.
来自褐色短杆菌（Brevibacterium fuscum）的高原儿茶酸（HPCA）2，3-双加氧酶（Fe-HPCD）在其活性位点中具有Fe（II）中心，其可以被Mn（II）或Co（II）取代。虽然Mn-HPCD表现出与Fe-HPCD相当的稳态动力学参数，但Co-HPCD的表现略有不同，表现出显著更高的KMO 2和kcat。Co-HPCD的高活性是令人惊讶的，因为钴具有三种金属中最高的标准M（III/II）氧化还原电位。比较的X-射线晶体结构的休息和底物结合的形式的Fe-，Mn-，和Co-HPCD表明，金属取代没有影响的本地配体环境，活性位点的构象完整性，或整体蛋白质结构，这表明蛋白质结构不差异调整的金属中心的潜力。Co-HPCD的稳态动力学分析表明，Co（II）中心改变了催化循环中中间体相互转化的相对速率常数，但仍然允许双加氧酶反应有效地进行。当与Fe-和Mn-HPCD的动力学数据相比，这些结果表明，双加氧酶催化可以在很宽的金属氧化还原电位范围内以高速率进行。这与提出的机制一致，其中金属介导邻苯二酚底物和O2之间的电子转移，形成假定的[M（II）（半醌）超氧]反应物质。这些动力学差异和光谱特性的Co-HPCD提供了新的工具，探索与extradiol双加氧酶家族相关的独特的O2激活机制。
Homoprotocatechuate (HPCA) 2,3-dioxygenase from Brevibacterium fuscum (Fe-HPCD) has an Fe(II) center in its active site that can be replaced with Mn(II) or Co(II). While Mn-HPCD exhibits steady state kinetic parameters comparable to those of Fe-HPCD, Co-HPCD behaves somewhat differently exhibiting a significantly higher KMO2 and kcat. The high activity of Co-HPCD is surprising, given that cobalt has the highest standard M(III/II) redox potential of the three metals. Comparison of the X-ray crystal structures of the resting and substrate-bound forms of Fe-, Mn-, and Co-HPCD shows that metal-substitution has no effect on the local ligand environment, the conformational integrity of the active site, or the overall protein structure, suggesting that the protein structure does not differentially tune the potential of the metal center. Analysis of the steady state kinetics of Co-HPCD suggests that the Co(II) center alters the relative rate constants for the interconversion of intermediates in the catalytic cycle but still allows the dioxygenase reaction to proceed efficiently. When compared with the kinetic data for Fe- and Mn-HPCD, these results show that dioxygenase catalysis can proceed at high rates over a wide range of metal redox potentials. This is consistent with the proposed mechanism in which the metal mediates electron transfer between the catechol substrate and O2 to form the postulated [M(II)(semiquinone)superoxo] reactive species. These kinetic differences and the spectroscopic properties of Co-HPCD provide new tools with which to explore the unique O2 activation mechanism associated with the extradiol dioxygenase family.
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影响因子：
2.9
作者：
Crawford, PA;Yang, KW;Crowder, MW
通讯作者：
Crowder, MW
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
3
作者：
Emerson, JP;Wagner, ML;Wackett, LP
通讯作者：
Wackett, LP
影响因子：
3.9
作者：
BENCINI, A;BERTINI, I;LUCHINAT, C
通讯作者：
LUCHINAT, C
影响因子：
2.9
作者：
Al-Mjeni, F;Ju, T;Maroney, MJ
通讯作者：
Maroney, MJ