Lignin peroxidase (LiP) is an important enzyme for degrading aromatic hydrocarbons not only in nature but also in industry. In the presence of H2O2, this enzyme can easily decompose lignin and analogue compounds under mild conditions. In this reaction mechanism, LiP catalyzes the C–C cleavage of a propenyl side chain, being able to produce veratraldehyde (VAD) from 1-(3′,4′-dimethoxyphenyl) propene (DMPP). One of the few and complete proposed mechanisms includes several non-enzymatic reactions. In this study, we performed a computational study to gain insight about the non-enzymatic steps involved in the reaction mechanism of VAD formation from DMPP using LiP as a catalyst. A kinetic characterization of the reaction using the reaction force and the reaction force constant concepts within the density functional theory (DFT) framework is proposed. All theoretical calculations for the reaction pathway were performed using the Minnesota Global Hybrid functional M06-2X and a 6-31++G(d,p) basis set. The complete reaction comprises seven steps (five steps not including LiP as a catalyst), which include radical species formation, bond transformation, water and oxygen addition, atom reordering, and deacetylation. The overall mechanism is an endothermic process with mixed activation energies depending on the four transition states. These results are the first attempt to fully understand the catalytic role of LiP in the degradation of lignin and its aromatic derivative compounds in terms of the electronic structure methods and future hybrid calculation approaches that we have recently been performing.

中文翻译：

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1-(3',4'-二甲氧基苯基)丙烯生成3,4-二甲氧基苯甲醛的反应机理

木质素过氧化物酶 (LiP) 是一种重要的酶，不仅在自然界中而且在工业中用于降解芳烃。在 H2O2 存在下，该酶可以在温和条件下轻松分解木质素和类似化合物。在该反应机制中，LiP 催化丙烯基侧链的 C-C 裂解，能够从 1-(3',4'-二甲氧基苯基) 丙烯 (DMPP) 生产藜芦醛 (VAD)。提出的为数不多且完整的机制之一包括几种非酶促反应。在这项研究中，我们进行了一项计算研究，以深入了解使用 LiP 作为催化剂从 DMPP 形成 VAD 的反应机制中涉及的非酶促步骤。提出了使用密度泛函理论 (DFT) 框架内的反作用力和反作用力常数概念的反应动力学表征。反应途径的所有理论计算均使用 Minnesota Global Hybrid 泛函 M06-2X 和 6-31++G(d,p) 基组进行。完整的反应包括七个步骤（五个步骤不包括 LiP 作为催化剂），其中包括自由基物种形成、键转换、水和氧加成、原子重新排序和脱乙酰化。整个机制是吸热过程，具有取决于四种过渡态的混合活化能。这些结果是首次尝试从我们最近进行的电子结构方法和未来混合计算方法方面全面了解 LiP 在降解木质素及其芳族衍生化合物中的催化作用。