HPPD的催化反应机理及其与抑制剂相互作用的研究

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is one of the most important targets for herbicide discovery. However, recently the toxicity of the commercialized HPPD inhibitors against the human health and environmental system is drawing more and more attention, due to their poor selectivity against different species of organisms. Therefore, it is challenging but very important to identify the structural differences between the HPPD of control weeds and HPPD from the other organisms such as human or mammals, which is believed to be highly important in herbicide discovery for crop protection. In addition, all the known HPPD inhibitors are competitive inhibitors. Thus, to understand the binding mode of the substrate (4-Hydroxyphenylpyruvate Acid, HPPA) and its comprehensive oxidation mechanism in HPPD is very essential for the design of novel HPPD inhibitors. In this project, the catalytic mechanism of HPPD and the chemical biology study about the interaction of HPPD from different species with inhibitors will be carried out by combining various disciplines and research techniques. Based on the above study, the binding modes of the substrate in HPPD will be identified, and the structural differences among the HPPD from different species as well as the comprehensive understanding about the interaction of small molecules with multi-species HPPD would be illustrated. Hopefully, the present project will facilitate the rational design of new HPPD inhibitors with novel scaffolds, and will gain the structural insight for exploring new HPPD-inhibiting herbicide leads with good selectivity and low ecotoxicity.

对羟基苯基丙酮酸双加氧酶（HPPD）是当前最重要的除草剂作用靶标之一。由于现有商品化HPPD抑制型除草剂的种属选择性低，其生态环境毒性问题已引起了人们的广泛关注。因此，搞清楚靶标物种HPPD（如杂草）和非靶标物种HPPD（如人和哺乳动物）之间的结构差异性，以及它们与小分子相互作用的差异性，是一项具有重要理论意义和实践价值的研究课题。从抑制类型来讲，现有HPPD抑制剂都属于底物HPPA的竞争性抑制剂，这就是说，设计新型的HPPD抑制剂就必须要弄清楚底物HPPA的结合方式及HPPD的催化反应机理。本项目拟综合多学科前沿技术，阐明底物在HPPD中的结合模式和动态催化过程，揭示不同种属HPPD的结构差异，深入理解抑制剂分子与多种属HPPD间相互作用的分子机制，从而为开展靶向HPPD的新型抑制剂的合理设计提供分子基础，也将为进一步开发具有低毒副作用的绿色HPPD抑制型除草剂提供理论指导。

对羟基苯基丙酮酸双加氧酶（HPPD）是当前最重要的除草剂作用靶标之一。由于现有商品化HPPD抑制型除草剂的种属选择性低，该类除草剂的生态环境毒性问题已引起了人们的广泛关注。因此，搞清楚靶物种HPPD（如杂草）和非靶标物种HPPD（如人和哺乳动物）之间的结构差异性，以及它们小分子相互作用的差异性，是一项具有重要理论意义和实践价值的研究课题。从作用机制来讲，现有HPPD抑制剂都属于底物HPPA的竞争性抑制剂，这就是说，设计新型的HPPD抑制剂就必须要弄清楚底物HPPA的结合方式及HPPD的酶催化反应机理。本项目执行期间，围绕“HPPD抑制剂合理设计的分子基础”这一关键科学问题，开展HPPD靶标组的构建、HPPD催化机理的研究，以及不同种属HPPD与抑制剂小分子相互作用的化学生物学研究。从分子水平上分别获得了拟南芥HPPD与底物对羟苯基丙酮酸（HPPA）和产物对羟基苯乙酸（HPA）的复合物晶体结构，进而阐明了底物分子如何进入HPPD活性空腔及具体的反应路径。在此基础上，深入比较不同种属HPPD的结构差异性，从生物化学和结构生物学方方面最终揭示它们与抑制剂小分子相互作用的差异性，为具有高效性和高种属选择性的新型HPPD抑制型除草剂的合理设计提供了坚实的结构基础。

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