State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic and Developmental Sciences, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
J Hazard Mater. 2023 Sep 5;457:131802. doi: 10.1016/j.jhazmat.2023.131802. Epub 2023 Jun 8.
As a phytotoxin and synthetic chemical, coumarin (COU) is known for its hepatotoxicity and carcinogenicity. However, no thorough characterization of its microbial degradation has been reported. Here, Pseudomonas sp. strain NyZ480 was isolated for its capability of utilizing COU as the sole carbon source. Studies on its growth and degradation efficiency of COU under various conditions suggested that strain NyZ480 performed the optimum degradation at 30 ℃, pH 7, and 0.5 mM COU was completely removed within 4 h with 1% inoculum. HPLC and LC-MS analyses indicated that dihydrocoumarin (DHC), melilotic acid (MA) and 3-(2,3-dihydroxyphenyl)propionate (DHPP) were the upstream biotransformation intermediates of COU. Enzyme assay established that the initial reaction transforming COU to DHC required an NAD(P)H-dependent reductase, followed by the hydrolysis of DHC to generate MA, and the third reaction catalyzing the monooxygenation of MA to DHPP utilized a strict NADH-dependent hydroxylase. Combining genomics and transcriptomics, we proposed that the COU downstream degradation (from DHPP) was catalyzed by enzymes encoded by a gene cluster homologous to the mhp cluster for 3(3-hydroxyphenyl)propionate degradation via DHPP in E. coli. This study thoroughly identified the intermediates from the COU catabolism, providing essential insights into the molecular evidences of its biodegradation pathway.
香豆素（COU）作为一种植物毒素和合成化学物质，以其肝毒性和致癌性而闻名。然而，目前还没有关于其微生物降解的全面描述。在这里，我们分离到一株能够利用 COU 作为唯一碳源的假单胞菌（Pseudomonas sp.）菌株 NyZ480。研究了该菌株在不同条件下的生长和 COU 降解效率，结果表明菌株 NyZ480 在 30℃、pH 值为 7 和 0.5mM COU 的条件下表现出最佳降解效果，在 1%接种量下，4 小时内可完全去除 COU。HPLC 和 LC-MS 分析表明，二氢香豆素（DHC）、乳清酸（MA）和 3-（2,3-二羟苯基）丙酸（DHPP）是 COU 上游生物转化的中间产物。酶活性测定表明，将 COU 转化为 DHC 的初始反应需要一种依赖 NAD(P)H 的还原酶，然后 DHC 水解生成 MA，第三反应是 MA 单加氧生成 DHPP，该反应需要严格依赖 NADH 的羟化酶。通过基因组学和转录组学分析，我们提出 COU 下游降解（从 DHPP 开始）是由编码酶的基因簇催化的，该基因簇与大肠杆菌中通过 DHPP 降解 3-(3-羟苯基)丙酸的 mhp 基因簇同源。本研究彻底鉴定了 COU 代谢途径中的中间产物，为其生物降解途径的分子证据提供了重要的见解。
