Abstract：
Natural estrogens, including estrone (E1), 17β-estradiol (E2), and estriol (E3), are potentially carcinogenic pollutants commonly found in water and soil environments. Bacterial metabolic pathway of E2 has been studied; however, the catabolic products of E3 have not been discovered thus far. In this study, Novosphingobium sp. ES2-1 was used as the target strain to investigate its catabolic pathway of E3. The metabolites of E3 were identified by high performance liquid chromatography-high resolution mass spectrometry (HPLC-HRMS) combined with stable 13C3-labeling. Strain ES2-1 could almost completely degrade 20 mg∙L-1 of E3 within 72 h under the optimal conditions of 30°C and pH 7.0. When inoculated with strain ES2-1, E3 was initially converted to E1 and then to 4-hydroxyestrone (4-OH-E1), which was then cleaved to HIP (metabolite A6) via the 4, 5-seco pathway or cleaved to the B loop via the 9,10-seco pathway to produce metabolite with a long-chain ketone structure (metabolite B4). Although the ring-opening sequence of the above two metabolic pathways was different, the metabolism of E3 was achieved especially through continuous oxidation reactions. This study reveals that, E3 could be firstly converted to E1 and then to 4-OH-E1, and finally degraded into small molecule metabolites through two alternative pathways, thereby reducing E3 pollution in water and soil environments.
摘要：
天然雌激素,包括雌酮(E1)，17β-雌二醇(E2),和雌三醇（E3），是水和土壤环境中常见的潜在致癌污染物。已经研究了E2的细菌代谢途径；然而，到目前为止，尚未发现E3的分解代谢产物。在这项研究中,Novoshingoumsp.以ES2-1为靶菌株研究其E3的分解代谢途径。通过高效液相色谱-高分辨率质谱（HPLC-HRMS）结合稳定的13C3标记鉴定E3的代谢物。在30°C和pH7.0的最佳条件下，菌株ES2-1可以在72h内几乎完全降解20mg·L-1的E3。当接种菌株ES2-1时，E3最初转化为E1，然后转化为4-羟基雌酮（4-OH-E1），然后通过4,5-seco途径裂解成HIP(代谢物A6)或通过9,10-seco途径裂解成B环,以产生具有长链酮结构的代谢物(代谢物B4)。虽然上述两种代谢途径的开环顺序不同,E3的代谢尤其是通过连续的氧化反应实现的。这项研究表明,E3可以先转化为E1，然后转化为4-OH-E1，最后通过两种途径降解为小分子代谢产物，从而减少水和土壤环境中的E3污染。
