The molecular mechanism of the photocatalytic oxidation reactions by horseradish peroxidase in the presence of histidine,Green Chemistry

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The molecular mechanism of the photocatalytic oxidation reactions by horseradish peroxidase in the presence of histidine
Green Chemistry ( IF 9.3 ) Pub Date : 2020-08-20 , DOI: 10.1039/d0gc01972k
Raheleh Ravanfar _{1,

2,

3,

4} , Alireza Abbaspourrad _{1,

2,

3,

4}

Affiliation

Oxidation reactions catalyzed by horseradish peroxidase (HRP) involve the conversion of ferric heme to the ferryl state by hydrogen peroxide (H₂O₂). As a result, HRP is typically considered unreactive without the presence of H₂O₂. Herein, we report the first use of histidine (His) and HRP in the presence of daylight and oxygen to initiate photocatalytic oxidation reactions without the addition of H₂O₂. We demonstrate that the oxidation reactions of norbixin (NBX) molecules proceed 2-times faster using this HRP/His system in comparison with HRP/H₂O₂. Most importantly, we also demonstrate that new species of NBX oxidized products are formed using HRP/His. In this work, we investigate the key steps of the HRP mechanism in the presence of His using electron paramagnetic resonance spectroscopy, liquid chromatography-mass spectrometry, and ultraviolet-visible spectrophotometry. Bearing in mind that H₂O₂ is normally thought indispensable for initiating the oxidation reactions of HRP, this work suggests a potential paradigm shift in our understanding of possible HRP mechanisms in the catalysis of biochemical reactions. The use of His, a natural essential amino acid, to mediate the formation of ferryl heme intermediates suggests the HRP/His system could serve as a natural catalyst for applications in photochemistry and bioelectrocatalysis.

中文翻译：

组氨酸存在下辣根过氧化物酶光催化氧化反应的分子机理

辣根过氧化物酶（HRP）催化的氧化反应包括通过过氧化氢（H ₂ O ₂）将铁血红素转化为亚铁状态。结果，在没有H ₂ O ₂的情况下，通常认为HRP是不反应的。本文中，我们报道了在日光和氧气存在下首次使用组氨酸（His）和HRP来引发光催化氧化反应，而无需添加H ₂ O ₂。我们证明了使用此HRP / His系统与HRP / H ₂ O ₂相比，norbixin（NBX）分子的氧化反应进行2倍快。最重要的是，我们还证明了使用HRP / His形成了新的NBX氧化产物。在这项工作中，我们使用电子顺磁共振波谱，液相色谱-质谱和紫外可见分光光度法研究存在His时HRP机理的关键步骤。记住H ₂ O ₂通常被认为是引发HRP氧化反应必不可少的，这项工作表明在我们对生化反应催化中可能的HRP机制的理解中，潜在的范式转移。使用His（一种天然必需氨基酸）来介导亚铁血红素中间体的形成表明，HRP / His系统可以用作光化学和生物电催化中的天然催化剂。

更新日期：2020-09-21

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