Degradation mechanisms of a nonphenolic β-O-4 lignin model dimer by Trametes versicolor laccase in the presence of 1-hydroxybenzotriazole
Degradation mechanisms of a nonphenolic β-O-4 lignin model dimer by Trametes versicolor laccase in the presence of 1-hydroxybenzotriazole
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DOI：
10.1016/s0141-0229(01)00523-3
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发表时间：
2002-04-16
影响因子：
3.4
通讯作者：
Ohashi, H
中科院分区：
文献类型：
--
作者：
Kawai, S;Nakagawa, M;Ohashi, H
过去的研究表明，花色曲霉漆酶催化Calpha-Cβ裂解，Calpha-氧化。在1-羟基苯并三唑存在下，非酚类β-O-4木质素模型二聚体1，3-dihydroxy-2-(2，6-dimethoxyphenoxy)-1-(4-ethoxy-3-methoxyphenyl)propane(1)的β-乙醚裂解和芳环裂解。在这项研究中，我们基于(H2O)-O-18和O-18(2)的掺入实验，研究了漆酶/1-羟基苯并三氮唑对底物I的这些途径的详细降解机理。底物I在(H2O)-O-18中的氧化导致O-18进入三个芳环裂解产物和一个β-乙醚裂解产物，这些结果与木质素过氧化物酶的结果一致。我们推测底物I的这些裂解是通过I的β-芳基自由基中间体进行的。然而，漆酶/1-羟基苯并三氮唑对I的Calpha-Cβ裂解产物是4-乙氧基-3-甲氧基苯甲酸，而木质素过氧化物酶的降解产物是4-乙氧基-3-甲氧基苯甲醛。显然，在底物I的氧化过程中，4-乙氧基-3-甲氧基苯甲酸中加入了一个O-18前O-18(2)原子，以确认反应中间体。我们进行了2-(2，6-dimethoxyphenoxy)-1-(4-ethoxy-3-methoxyphenyl)-3-hydroxypropanone与碱性过氧化氢的化学反应。由于预期的过氧化氢中间体与I的苄基自由基与O-2反应生成的中间体非常相似，因此结果表明，主要的降解产物是4-乙氧基-3-甲氧基苯甲酸。因此，我们提出了通过漆酶/1-羟基苯并三氮唑对非酚类β-O-4木质素模型二聚体的Baeyer-Villiger反应进行新型的Calpha-Cβ裂解。(C)2002 Elsevier Science Inc.保留所有权利。
Past studies have shown that Trametes versicolor laccase catalyzed Calpha-Cbeta cleavage, Calpha-oxidation. beta-ether cleavage and aromatic ring cleavage of a nonphenolic beta-O-4 lignin model dimer, 1,3-dihydroxy-2-(2,6-dimethoxyphenoxy)-1-(4-ethoxy-3-methoxyphenyl)propane (1), in the presence of 1-hydroxybenzotriazole. In this study, we investigated the detailed degradation mechanism for these pathways of substrate I by laccase/1-hydroxybenzotriazole couple, based on incorporation experiments from (H2O)-O-18 and O-18(2). Oxidation of substrate I in (H2O)-O-18 resulted in the incorporation of O-18 into three aromatic ring cleavage products and a beta-ether cleavage product, These results were identical with those for lignin peroxidase. We infer-red that these cleavages of substrate I proceed via the beta-aryl cation radical intermediate of I. However, the Calpha-Cbeta cleavage degradation product of I by the laccase/1-hydroxybenzotriazole couple was 4-ethoxy-3-methoxybenzoic acid, whereas it was 4-ethoxy-3-methoxybenzaldehyde for lignin peroxidase. It is clear that one atom of O-18 front O-18(2) was incorporated into 4-ethoxy-3-methoxybenzoic acid during the oxidation of substrate I. To confirm the reaction intermediate. we carried out the chemical reaction of 2-(2,6-dimethoxyphenoxy)-1-(4-ethoxy-3-methoxyphenyl)-3-hydroxypropanone with alkaline hydrogen peroxide. since the expected hydroperoxide intermediate is quite similar to that formed from the reaction between the benzylic radical of I and O-2 The result showed that the main degradation product was 4-ethoxy-3-methoxybenzoic acid. Thus, we propose it novel Calpha-Cbeta cleavage via a kind of Baeyer-Villiger reaction for nonphenolic beta-O-4 lignin model dimer by laccase/1-hydroxybenzotriazole couple. (C) 2002 Elsevier Science Inc. All rights reserved.