Horseradish peroxidase (HRP) has demonstrated high activity for the modification of lignin. In this paper, several lignin model compounds with different functional groups and linkages are selected to investigate the reactivity of HRP-catalyzed lignin modification. The phenolic groups of lignin model compounds are indispensable for the HRP-catalyzed modification process. The introduction of the sulfomethylated methyl group or methoxyl group could facilitate or inhibit the modification, respectively. The oxidative coupling activity of α-O-4 lignin model compounds is higher than that of β-O-4 compounds. Meanwhile, the free energy obtained by density functional theory (DFT) is used to verify the results of the experimental study, and the order of preference for linkages is β-5 > β-β > β-O-4 in most cases. In addition, electron cloud density and steric hindrance of lignin model compounds have crucial effects on the oxidation and modification processes. Finally, the mechanism of HRP-catalyzed lignin modification is proposed.

中文翻译：

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辣根过氧化物酶催化木质素修饰机理的模型化合物研究。

辣根过氧化物酶（HRP）已证明对木质素的修饰具有很高的活性。本文选择了几种具有不同官能团和键的木质素模型化合物来研究HRP催化的木质素修饰的反应性。木质素模型化合物的酚基对于HRP催化的修饰过程是必不可少的。磺甲基化的甲基或甲氧基的引入可以分别促进或抑制修饰。α-O-4木质素模型化合物的氧化偶联活性高于β-O-4化合物。同时，通过密度泛函理论（DFT）获得的自由能被用于验证实验研究的结果，在大多数情况下，对键的优先顺序为β-5>β-β>β-O-4。此外，木质素模型化合物的电子云密度和空间位阻对氧化和修饰过程具有关键影响。最后提出了HRP催化木质素修饰的机理。