Faculty of Agriculture, Meijo University, Nagoya, Japan.
Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
Appl Environ Microbiol. 2024 Feb 21;90(2):e0175323. doi: 10.1128/aem.01753-23. Epub 2024 Jan 23.
White-rot fungi, such as , are the most efficient degraders of lignin, a major component of plant biomass. Enzymes produced by these fungi, such as lignin peroxidases and manganese peroxidases, break down lignin polymers into various aromatic compounds based on guaiacyl, syringyl, and hydroxyphenyl units. These intermediates are further degraded, and the aromatic ring is cleaved by 1,2,4-trihydroxybenzene dioxygenases. This study aimed to characterize homogentisate dioxygenase (HGD)-like proteins from that are strongly induced by the G-unit fragment of vanillin. We overexpressed two homologous recombinant HGDs, PcHGD1 and PcHGD2, in . Both PcHGD1 and PcHGD2 catalyzed the ring cleavage in methoxyhydroquinone (MHQ) and dimethoxyhydroquinone (DMHQ). The two enzymes had the highest catalytic efficiency (/) for MHQ, and therefore, we named PcHGD1 and PcHGD2 as MHQ dioxygenases 1 and 2 (PcMHQD1 and PcMHQD2), respectively, from . This is the first study to identify and characterize MHQ and DMHQ dioxygenase activities in members of the HGD superfamily. These findings highlight the unique and broad substrate spectra of PcHGDs, rendering them attractive candidates for biotechnological applications.IMPORTANCEThis study aimed to elucidate the properties of enzymes responsible for degrading lignin, a dominant natural polymer in terrestrial lignocellulosic biomass. We focused on two homogentisate dioxygenase (HGD) homologs from the white-rot fungus, , and investigated their roles in the degradation of lignin-derived aromatic compounds. In the genome database, PcMHQD1 and PcMHQD2 were annotated as HGDs that could cleave the aromatic rings of methoxyhydroquinone (MHQ) and dimethoxyhydroquinone (DMHQ) with a preference for MHQ. These findings suggest that MHQD1 and/or MHQD2 play important roles in the degradation of lignin-derived aromatic compounds by . The preference of PcMHQDs for MHQ and DMHQ not only highlights their potential for biotechnological applications but also underscores their critical role in understanding lignin degradation by a representative of white-rot fungus, .
白腐真菌，如 ，是木质素（植物生物质的主要成分）最有效的降解者。这些真菌产生的酶，如木质素过氧化物酶和锰过氧化物酶，将木质素聚合物分解成基于愈创木基、丁香基和对羟基苯基单元的各种芳香族化合物。这些中间产物进一步降解，芳香环被 1,2,4-三羟基苯二氧杂环己烷二加氧酶裂解。本研究旨在从 中鉴定和表征受香草基 G 片段强烈诱导的 homogentisate 双加氧酶（HGD）样蛋白。我们在 中过表达了两种同源重组 HGD，PcHGD1 和 PcHGD2。PcHGD1 和 PcHGD2 均催化甲氧基氢醌（MHQ）和二甲氧基氢醌（DMHQ）的环裂解。这两种酶对 MHQ 的催化效率（/）最高，因此，我们将 PcHGD1 和 PcHGD2 分别命名为 MHQ 双加氧酶 1 和 2（PcMHQD1 和 PcMHQD2），来自 。这是首次在 HGD 超家族成员中鉴定和表征 MHQ 和 DMHQ 双加氧酶活性的研究。这些发现强调了 PcHGDs 独特而广泛的底物谱，使其成为生物技术应用的有吸引力的候选者。
重要性
本研究旨在阐明负责降解木质素的酶的性质，木质素是陆地木质纤维素生物质中主要的天然聚合物。我们专注于白腐真菌 中的两个 homogentisate 双加氧酶（HGD）同源物，并研究了它们在木质素衍生芳香族化合物降解中的作用。在 基因组数据库中，PcMHQD1 和 PcMHQD2 被注释为 HGD，它们可以优先裂解甲氧基氢醌（MHQ）和二甲氧基氢醌（DMHQ）的芳环。这些发现表明，MHQD1 和/或 MHQD2 在 降解木质素衍生芳香族化合物中发挥重要作用。PcMHQDs 对 MHQ 和 DMHQ 的偏好不仅突出了它们在生物技术应用中的潜力，还强调了它们在理解白腐真菌代表物木质素降解中的关键作用。
