Peroxidase versus Peroxygenase Activity: Substrate Substituent Effects as Modulators of Enzyme Function in the Multifunctional Catalytic Globin Dehaloperoxidase.
Peroxidase versus Peroxygenase Activity: Substrate Substituent Effects as Modulators of Enzyme Function in the Multifunctional Catalytic Globin Dehaloperoxidase.
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DOI：
10.1021/acs.biochem.8b00540
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发表时间：
2018-06
期刊：
影响因子：
2.9
通讯作者：
A. McGuire;L. Carey;V. de Serrano;S. Dali;R. Ghiladi
中科院分区：
文献类型：
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作者：
A. McGuire;L. Carey;V. de Serrano;S. Dali;R. Ghiladi
脱卤过氧化物酶-血红蛋白（DHP）是一种多功能血红蛋白，可通过过氧化酶和/或过氧化酶机制催化多种底物的氧化，包括环/硝基酚、卤吲哚和吡咯。为了探讨底物取代基是否可以调节DHP酶活性，我们研究了在a . ornata生活的底栖环境中，在天然/卤化和非天然/人为来源的情况下，DHP对一组邻愈木酚底物的反应性。通过光谱、光谱和结构研究支持的生化分析，发现DHP可以催化4-卤代愈木酚（F、Cl和Br）的h2o2依赖性氧化脱卤成2-甲氧基苯醌（2-MeOBQ）。18O标记研究证实，O原子的掺入完全来自于水，与底物氧化通过过氧化物酶为基础的机制一致。2-MeOBQ产物进一步将DHP还原为氧化亚铁态，在底物氧化和DHP的O2载体功能之间提供了联系。非原生底物导致初始底物聚合，氧化程度不同，2-MeOBQ被鉴定为次要产物。当与先前研究的酚类底物的反应性一起观察时，本文的结果表明，在这种多功能催化珠蛋白中，简单的取代基效应可以作为过氧化物酶和过氧酶活性之间的功能开关。更广泛地说，如果将最近关于DHP与硝基酚和唑活性的研究结果包括在内，本文提出的结果进一步证明了人为来源的杂环化合物的广度，这些杂环化合物可能会破坏海洋血红蛋白或作为环境应激源，这些发现在评估这些污染物（及其代谢物）对水生系统的环境影响时可能很重要。
The dehaloperoxidase-hemoglobin (DHP) from the terebellid polychaete Amphitrite ornata is a multifunctional hemoprotein that catalyzes the oxidation of a wide variety of substrates, including halo/nitrophenols, haloindoles, and pyrroles, via peroxidase and/or peroxygenase mechanisms. To probe whether substrate substituent effects can modulate enzyme activity in DHP, we investigated its reactiviy against a panel of o-guaiacol substrates given their presence (from native/halogenated and non-native/anthropogenic sources) in the benthic environment that A. ornata inhabits. Using biochemical assays supported by spectroscopic, spectrometric, and structural studies, DHP was found to catalyze the H2O2-dependent oxidative dehalogenation of 4-haloguaiacols (F, Cl, and Br) to 2-methoxybenzoquinone (2-MeOBQ). 18O labeling studies confirmed that O atom incorporation was derived exclusively from water, consistent with substrate oxidation via a peroxidase-based mechanism. The 2-MeOBQ product further reduced DHP to its oxyferrous state, providing a link between the substrate oxidation and O2 carrier functions of DHP. Nonnative substrates resulted in polymerization of the initial substrate with varying degrees of oxidation, with 2-MeOBQ identified as a minor product. When viewed alongside the reactivity of previously studied phenolic substrates, the results presented here show that simple substituent effects can serve as functional switches between peroxidase and peroxygenase activities in this multifunctional catalytic globin. More broadly, when recent findings on DHP activity with nitrophenols and azoles are included, the results presented here further demonstrate the breadth of heterocyclic compounds of anthropogenic origin that can potentially disrupt marine hemoglobins or function as environmental stressors, findings that may be important when assessing the environmental impact of these pollutants (and their metabolites) on aquatic systems.