Magnetic spin effects in enzymatic reactions: Radical oxidation of NADH by horseradish peroxidase
Magnetic spin effects in enzymatic reactions: Radical oxidation of NADH by horseradish peroxidase
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DOI：
10.1021/ja0585735
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发表时间：
2006-07-05
影响因子：
15
通讯作者：
Grissom, Charles B.
中科院分区：
文献类型：
--
作者：
Afanasyeva, Maria S.;Taraban, Marc B.;Grissom, Charles B.
辣根过氧化物酶（HRP）催化氧化NADH的基本步骤的描述，沿着与磁场的酶促反应的依赖性的定量分析。在不存在H2O2的情况下，催化循环开始于从NADH到天然HRP的单电子转移，以形成NADH（中心点+）自由基阳离子和铁过氧化物酶中间体（Per（2+））。对磁场依赖的自由基对复合的理论框架进行了扩展，以描述磁场依赖的反应速率常数的多自旋顺磁对，包括NADH（中心点+）自由基阳离子和Per（2+），存在于一个相关的四重电子自旋状态。实验观察到的和理论计算的有效速率常数的磁场依赖性之间的良好协议强调了初始的单电子转移步骤的重要性，并支持一个模型，其中的催化循环开始与一个电子还原HRP的NADH。
A description of the elementary steps of the horseradish peroxidase (HRP)-catalyzed oxidation of NADH is presented, along with a quantitative analysis of the magnetic-field dependence of the enzymatic reaction. In the absence of H2O2, the catalytic cycle begins with single-electron transfer from NADH to native HRP to form the NADH(center dot+) radical cation and the ferroperoxidase intermediate (Per(2+)). The theoretical framework for the magnetic-field dependent recombination of radical pairs has been extended to describe the magnetic-field dependence of reaction rate constants for multi-spin paramagnetic pairs, including the NADH(center dot+) radical cation and Per(2+) that exist in a correlated quartet electronic spin state. Good agreement between the experimentally observed and the theoretically calculated magnetic-field dependences of the effective rate constants underlines the importance of the initial single-electron-transfer step and supports a model in which the catalytic cycle begins with the one-electron reduction of HRP by NADH.