De Guzman Lyle Ijssel P, Carpina Renato C, Chua Joan Catherine A, Yu Eizadora T
Institute of Chemistry, University of the Philippines Diliman, Quezon City, Philippines.
Marine Science Institute, University of the Philippines Diliman, Quezon City, Philippines.
Bioresour Bioprocess. 2025 May 6;12(1):42. doi: 10.1186/s40643-025-00876-7.
Carbohydrate-active enzymes (CAZymes) are crucial in the sustainable production of fuels and raw materials from recalcitrant plant cell wall polysaccharides (PCWPs). Teredinibacter turnerae, a symbiont of wood-boring shipworms, is a prolific degrader of plant biomass, largely due to the extensive CAZyme repertoire in its genome. To identify key enzymes involved in PCWP utilization, we analyzed the secretomes of T. turnerae E7MBN strain grown on sucrose, major PCWPs (cellulose, xylan, and pectin), and residual rice hull biomass using mass spectrometry-based proteomics. Our results show that T. turnerae E7MBN exhibits minimal enzyme secretion across various carbon sources, where secretomes mostly display similar functional profiles. Enzymatic complexity varied with the substrate, with cellulose-grown secretome being the most complex and comprising the majority of secreted CAZymes. These CAZymes contain domains that primarily target cellulose, hemicellulose, or pectin, notably including multicatalytic enzymes that are consistently found in the secretome and are likely central to biomass degradation. In contrast, the xylan-grown secretome displayed a more specific response, secreting only a single bifunctional hemicellulase, E7_MBN_00081, also identified as a core component of the bacteria's enzymatic repertoire. Meanwhile, the pectin-grown secretome consists of multiple tonB-dependent receptors, which, along with isomerases, are considered common secretome constituents. E7MBN also demonstrated the capability to utilize rice hull biomass, predominantly secreting proteins previously identified under cellulose. Protein-protein interaction network analysis further revealed functional associations between CAZymes and several uncharacterized proteins, which include CBM-containing redox enzymes and a putative xylan-acting protein, thus offering new insights into their potential role in lignocellulose degradation. Overall, our work contributes to our understanding of enzymatic strategies employed by T. turnerae for PCWP deconstruction and highlights its potential as a promising source of CAZymes for sustainable biomass conversion.
碳水化合物活性酶（CAZymes）在从难降解的植物细胞壁多糖（PCWPs）可持续生产燃料和原材料方面至关重要。特纳氏食木菌（Teredinibacter turnerae）是钻木船蛆的一种共生菌，是植物生物质的高效降解者，这主要归功于其基因组中丰富的CAZyme库。为了鉴定参与PCWP利用的关键酶，我们使用基于质谱的蛋白质组学分析了在蔗糖、主要PCWPs（纤维素、木聚糖和果胶）以及稻壳残余生物质上生长的特纳氏食木菌E7MBN菌株的分泌蛋白组。我们的结果表明，特纳氏食木菌E7MBN在各种碳源上的酶分泌极少，其分泌蛋白组大多显示出相似的功能谱。酶的复杂性因底物而异，以纤维素为底物生长的分泌蛋白组最为复杂，且包含了大部分分泌的CAZymes。这些CAZymes包含主要靶向纤维素、半纤维素或果胶的结构域，特别是包括在分泌蛋白组中始终存在且可能对生物质降解至关重要的多催化酶。相比之下，以木聚糖为底物生长的分泌蛋白组表现出更具特异性的反应，仅分泌一种双功能半纤维素酶E7_MBN_00081，该酶也被鉴定为该细菌酶库的核心成分。同时，以果胶为底物生长的分泌蛋白组由多种tonB依赖性受体组成，这些受体与异构酶一起被认为是常见的分泌蛋白组成成分。E7MBN还展示了利用稻壳生物质的能力，主要分泌先前在以纤维素为底物生长时鉴定出的蛋白质。蛋白质 - 蛋白质相互作用网络分析进一步揭示了CAZymes与几种未表征蛋白质之间的功能关联，其中包括含CBM的氧化还原酶和一种假定的木聚糖作用蛋白，从而为它们在木质纤维素降解中的潜在作用提供了新的见解。总体而言，我们的工作有助于我们理解特纳氏食木菌用于解构PCWP的酶策略，并突出了其作为可持续生物质转化中CAZymes的有前景来源的潜力。
