State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, PR China; University of the Chinese Academy of Sciences, Beijing 100049, PR China.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, PR China; University of the Chinese Academy of Sciences, Beijing 100049, PR China.
Environ Int. 2024 Aug;190:108906. doi: 10.1016/j.envint.2024.108906. Epub 2024 Jul 24.
The extensive use of sulfonylurea herbicides has raised major concerns regarding their long-term soil residues and agroecological risks despite their role in agricultural protection. Microbial degradation is an important approach to remove sulfonylureas, whereas understanding the associated biodegradation mechanisms, enzymes, and physiological responses remains incomplete. Based on the rapid biodegradation of nicosulfuron by typical fungal isolate Talaromyces flavus LZM1, the dependency on cellular accumulation and environmental conditions, e.g. pH and nutrient supplies, was shown in the study. The biodegradation of nicosulfuron occurred intracellularly and followed the cascade of reactions including hydrolysis, Smile contraction rearrangement, hydroxylation, and opening of the pyrimidine ring. Besides 2-amino-4,6-dimethoxypyrimidine (ADMP) and 2-aminosulfonyl-N,N-dimethylnicotinamide (ASDM), numerous products and intermediates were newly identified and the structural forms of methoxypyrimidine and sulfonylurea bridge contraction rearrangement are predicted to be more toxic than nicosulfuron. The biodegradation should be enzymatically regulated by glycosylphosphatidylinositol transaminase (GPI-T) and P450s, which were manifested with the significant upregulation in proteomics. It is the first time that the hydrolysis of nicosulfuron into ADMP and ASDM have been associated with GPI-T. The integrated pathways of biodegradation were further elucidated through the involvement of various active enzymes. Except for the enzymatic catalysis, the physiological responses verified by metabolo-proteomics were critical not only to regulate material synthesis, uptake, utilization, and energy transfer but also to maintain antioxidant homeostasis, biodegradability, and tolerance of nicosulfuron by the differentially expressed metabolites, such as acetolactate synthase and 3-isopropylmalate dehydratase. The obtained results would help understand the biodegradation mechanism of sulfonylurea from chemicobiology and enzymology and promote the use of fungal biodegradation in pollution rehabilitation.
磺酰脲类除草剂的广泛使用引起了人们对其在农业保护中土壤残留和农业生态风险的极大关注。微生物降解是去除磺酰脲类化合物的重要途径，然而，对相关生物降解机制、酶和生理响应的理解仍不完整。基于典型真菌分离株塔宾曲霉 LZM1 对烟嘧磺隆的快速生物降解，本研究表明其对细胞积累和环境条件（如 pH 和养分供应）的依赖性。烟嘧磺隆的生物降解发生在细胞内，并遵循一系列反应，包括水解、Smile 收缩重排、羟化和嘧啶环的开环。除了 2-氨基-4,6-二甲氧基嘧啶（ADMP）和 2-氨基磺酰基-N,N-二甲基烟酰胺（ASDM）外，还新鉴定了许多产物和中间体，并且预测甲氧嘧啶和磺酰脲桥收缩重排的结构形式比烟嘧磺隆更具毒性。生物降解应该通过糖基磷脂酰肌醇转氨酶（GPI-T）和 P450s 进行酶调节，这在蛋白质组学中表现出显著的上调。这是首次将烟嘧磺隆水解为 ADMP 和 ASDM 与 GPI-T 相关联。通过涉及各种活性酶，进一步阐明了生物降解的综合途径。除了酶催化作用外，代谢组学验证的生理响应不仅对调节物质合成、吸收、利用和能量转移至关重要，而且对维持烟嘧磺隆的抗氧化稳态、生物降解性和耐受性也至关重要，如乙酰乳酸合酶和 3-异戊烯基苹果酸脱水酶。这些结果将有助于从化学生物学和酶学角度理解磺酰脲类化合物的生物降解机制，并促进真菌生物降解在污染修复中的应用。
