Liang Congying, Lin Lu, Xu Tao, Kang Guoqiang, Liu Zhi-Hua, Li Bing-Zhi
Institute of Marine Science and Technology, Shandong University, Qingdao 266237, People's Republic of China.
Frontiers Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, People's Republic of China.
Proc Natl Acad Sci U S A. 2025 Jan 28;122(4):e2417343122. doi: 10.1073/pnas.2417343122. Epub 2025 Jan 24.
Lignin degradation by biocatalysts is a key strategy to develop a plant-based sustainable carbon economy and thus alleviate global climate change. This process involves synergy between ligninases and auxiliary enzymes. However, auxiliary enzymes within secretomes, which are composed of thousands of enzymes, remain enigmatic, although several ligninolytic enzymes have been well characterized. Moreover, it is a challenge to understand synergistic lignin degradation via a diverse array of enzymes, especially in bacterial systems. In this study, the coexpression network of the periplasmic proteome uncovers potential accessory enzymes for B-type dye-decolorizing peroxidases (DypBs) in A514. The catalytic network of the DypBs-based multienzyme complex is characterized. DypBs couple with quinone reductases and nitroreductase to participate in quinone redox cycling. They work with superoxide dismutase to induce Fenton reaction for lignin oxidation. A synthetic enzyme cocktail (SEC), recruiting 15 enzymes, was consequently designed with four functions. It overcomes the limitation of lignin repolymerization, exhibiting a capacity comparable to that of the native periplasmic secretome. Importantly, we reveal the synergistic mechanism of a SEC-A514 cell system, which incorporates the advantages of in vitro enzyme catalysis and in vivo microbial catabolism. Chemical analysis shows that this system significantly reduces the molecular weight of lignin, substantially extends the degradation spectra for lignin functional groups, and efficiently metabolizes lignin derivatives. As a result, 25% of lignin is utilized, and its average molecular weight is reduced by 27%. Our study advances the knowledge of bacterial lignin-degrading multienzymes and provides a viable lignin degradation strategy.
生物催化剂降解木质素是发展基于植物的可持续碳经济从而缓解全球气候变化的关键策略。这一过程涉及木质素酶与辅助酶之间的协同作用。然而，尽管几种木质素降解酶已得到充分表征，但由数千种酶组成的分泌蛋白组中的辅助酶仍然神秘莫测。此外，理解通过多种酶进行的协同木质素降解是一项挑战，尤其是在细菌系统中。在本研究中，周质蛋白质组的共表达网络揭示了A514中B型染料脱色过氧化物酶（DypBs）的潜在辅助酶。对基于DypBs的多酶复合物的催化网络进行了表征。DypBs与醌还原酶和硝基还原酶偶联参与醌氧化还原循环。它们与超氧化物歧化酶协同作用以诱导芬顿反应来氧化木质素。因此，设计了一种招募15种酶的合成酶混合物（SEC），具有四种功能。它克服了木质素再聚合的限制，表现出与天然周质分泌蛋白组相当的能力。重要的是，我们揭示了SEC - A514细胞系统的协同机制，该系统结合了体外酶催化和体内微生物分解代谢的优点。化学分析表明，该系统显著降低了木质素的分子量，大幅扩展了木质素官能团的降解谱，并有效代谢了木质素衍生物。结果，25%的木质素被利用，其平均分子量降低了27%。我们的研究推进了对细菌木质素降解多酶的认识，并提供了一种可行的木质素降解策略。
