Substrate-assisted O2 activation in a cofactor-independent dioxygenase.
Substrate-assisted O2 activation in a cofactor-independent dioxygenase.
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DOI：
10.1016/j.chembiol.2013.11.013
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发表时间：
2014-02
影响因子：
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通讯作者：
S. Thierbach;N. Bui;J. Zapp;S. R. Chhabra;R. Kappl;S. Fetzner
中科院分区：
文献类型：
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作者：
S. Thierbach;N. Bui;J. Zapp;S. R. Chhabra;R. Kappl;S. Fetzner
与大多数依赖于有机辅因子或金属离子进行催化的 O2 激活酶相反，一组特定的结构上不相关的加氧酶无需任何辅因子即可发挥功能。在本研究中，我们表征了具有 α/β-水解酶折叠的不依赖于辅因子的双加氧酶反应途径中 O2 激活的机制，该双加氧酶催化 2-烷基-3-羟基-4(1H)-喹诺酮类药物的氧解裂解。化学分析和电子顺磁共振波谱数据表明，酶活性位点中的 O2 激活是底物辅助的，依赖于从结合的底物阴离子到 O2 的单电子转移形成自由基对，该自由基对重新组合成 C2-过氧化物中间体。因此，如果有机底物本身在被活性位点碱激活为（碳）阴离子后本质上对分子氧具有反应性，则加氧酶可以在没有辅因子的情况下发挥作用。
In contrast to the majority of O2-activating enzymes, which depend on an organic cofactor or a metal ion for catalysis, a particular group of structurally unrelated oxygenases is functional without any cofactor. In this study, we characterized the mechanism of O2activation in the reaction pathway of a cofactor-independent dioxygenase with an α/β-hydrolase fold, which catalyzes the oxygenolytic cleavage of 2-alkyl-3-hydroxy-4(1H)-quinolones. Chemical analysis and electron paramagnetic resonance spectroscopic data revealed that O2activation in the enzyme's active site is substrate-assisted, relying on single electron transfer from the bound substrate anion to O2to form a radical pair, which recombines to a C2-peroxide intermediate. Thus, an oxygenase can function without a cofactor, if the organic substrate itself, after activation to a (carb)anion by an active-site base, is intrinsically reactive toward molecular oxygen.