Discovery of catalytic tools for isoprenoid production

类异戊二烯是一大类结构多样的天然产物，已知化合物超过55000种。许多类异戊二烯已被用作香料、药品和工业聚合物。目前所有的类异戊二烯都是通过植物提纯或涉及石油化工的化学合成来提供的。然而，天然来源的产量往往不足以满足工业需求，而且由于环境干扰，化学合成是不可取的。为了克服这些问题，利用生物系统酶法生产类异戊二烯已成为传统纯化和化学合成的一种有吸引力的替代方法；然而，我们目前对类异戊二烯代谢的了解仍然不足以实现类异戊二烯的生物供应。******我的研究计划的长期目标是通过可持续的生物方法提供类异戊二烯产品，从而取代石化衍生产品。为了提高对类异戊二烯代谢的认识，我建议研究类异戊二烯天然产物的两个亚类——倍半萜内酯（SLs）和天然橡胶（NR）。SLs已被用作许多药物的基石，而NR是数百种工业产品不可或缺的生物聚合物。SL和NR生物合成的确切机制尚不清楚，将采用生物化学、遗传学和基因组学相结合的综合方法来阐明SL和NR生物合成的奥秘。******首先，我们将通过从两种药用植物中分离和鉴定酶来研究自然界中各种SLs的立体选择性生物合成是如何实现的。立体选择性合成化学物质在制药工业中是必不可少的，因此这项工作将为生产立体选择性化学物质提供生物学方法。其次，基于我们在SL生物合成中发现的一种混杂酶，我们将尝试在微生物中组合使用植物酶来生产自然界中不存在的新型SL。将在酵母中合成100多种酶的组合，并鉴定和纯化新的SL产品以进行结构研究。最终，这些新的SLs将被检测可能的抗菌活性。第三，由于我们不完全了解NR是如何在植物中生物合成的，部分原因是我们对NR途径中几种蛋白质成分的知识存在空白，因此将使用生化和遗传方法从植物中识别和表征NR生物合成所需的其他蛋白质。新发现的蛋白质成分可用于设计可在热带拟橡胶树外生产NR的替代生物系统，从而确保聚合物的可持续性。总的来说，拟议的研究将为我们社会急需的类异戊二烯产品的可持续供应奠定知识基础

The isoprenoids are a large and structurally diverse class of natural products with more than 55,000 known compounds. Many isoprenoids have been used as flavors, pharmaceuticals, and industrial polymers. All isoprenoids are currently supplied either by purification from plants or by chemical synthesis involving petrochemicals. However, the yield from natural sources is often inadequate to meet industrial demands, and chemical synthesis is not desirable due to environmental perturbation. To overcome these, the enzymatic production of isoprenoids using biological systems has become an attractive alternative to the traditional purification and chemical synthesis; however, our current knowledge of isoprenoid metabolism remains insufficient to realize the biological supply of isoprenoids. ******The long-term goal of my research program is to supply isoprenoid products by sustainable biological methods, thus replacing the petrochemical-derived products. To advance the knowledge of isoprenoid metabolism, I propose to study two subclasses of isoprenoid natural products - sesquiterpene lactones (SLs) and natural rubber (NR). SLs have been used as building blocks for many pharmaceuticals while NR is an indispensable biopolymer for hundreds of industrial products. Precise mechanisms of SL and NR biosynthesis remain elusive, and integrative approaches combining biochemistry, genetics, and genomics will be used to elucidate the mysteries of SL and NR biosynthesis. ******First, how stereoselective biosynthesis of various SLs is achieved in nature will be studied by isolating and characterizing enzymes from two medicinal plant species. Stereoselective synthesis of chemicals is essential in the pharmaceutical industry, and thus this work will provide biological methods to produce stereoselective chemicals. Second, combinatorial uses of plant enzymes will be attempted in microbes to produce novel SLs that are not present in nature, based on our discovery of one promiscuous enzyme in SL biosynthesis. More than 100 combinations of enzymes will be synthetically made in yeast, and the resulting new SL products will be identified and purified for structural studies. Ultimately, these new SLs will be examined for possible anti-bacterial activities. Third, as we do not fully understand how NR is biosynthesized in plants, in part due to gaps in our knowledge of several protein components in the NR pathway, additional necessary proteins for NR biosynthesis will be identified and characterized from plants using biochemical and genetic approaches. The newly identified protein component(s) can be used to devise alternative bio-systems that can produce NR outside of the tropical para-rubber trees, thereby securing polymer sustainability. Collectively, the proposed research will lay a foundation of knowledge for a sustainable supply of isoprenoid products critically needed in our society.**