Structural and Functional Analysis of the Plant Phenylpropanoid Biosynthetic Pathway

植物苯丙素类化合物包括黄酮类和二苯乙烯类化合物，它们是一类结构多样的次生代谢物，在植物与周围环境的相互作用中发挥着重要作用。这些化合物在植物中的用途多种多样，包括作为结构聚合物、防御屏障、响应微生物、昆虫和食草动物捕食而合成的防御化学物质、固氮根瘤菌的信号分子、紫外线保护剂和色素。除了在植物生理学中的作用外，苯丙烷类化合物还具有许多已被证明对制药、食品、农业和营养业有用的特性。这个项目的一个主要目标是了解植物苯丙烷类化合物生物合成的分子机制。本研究的目的是通过X射线结晶学和酶学研究，研究查尔酮合成酶(CHS)/二苯乙烯合成酶(STS)超家族的功能多样性，查尔酮异构酶(CHI)在查尔酮和脱氧查尔酮生物合成途径中介导的黄烷酮形成的机制、立体化学和选择性，查尔酮还原酶(CHR)的结构和机制，以及在类黄酮和类黄酮生物合成过程中查尔酮、CHI和/或CHR多酶复合体形成的能量和结构特征。这些研究将阐明控制植物类苯丙烷产生的机制，特别是将这些途径的生物合成多样性与导致这种生物重要形式的化学多样性的持续进化变化联系起来。值得注意的是，拟议的研究活动产生了更广泛的影响，其中包括一个重要的培训部分，即研究生(博士)和本科生(学士)都可以单独参加科学研究中具有代表性的群体。此外，这项研究产生的关键科学发现将主要通过每年一次的讲座向公众传播，讲座通过为公众举办的晚间系列研讨会，以非专业的术语讨论索尔克研究所正在进行的公共支持工作的科学和意义。最近，在该项目的初始阶段获得的关键发现描述了了解植物次生代谢对人类在农业、疾病预防和药物开发方面的好处。许多植物来源的苯丙烷类化合物都是有价值的药物。此外，经常食用苯丙烷类化合物，包括木脂素、二苯乙烯类和(Iso)黄酮类化合物，对健康有相当大的好处，包括降低癌症和冠状动脉疾病的风险因素。植物用来产生这些小分子的酶支架是利用包括结构生物学和基因组学在内的新方法为药物发现创造新的分子实体的新颖和有用的起点。最重要的是，所有生物都利用化学多样性在恶劣和具有挑战性的环境中生存和繁荣。在过去的几年里，尽管生物体的蛋白质和基因多样性吸引了公众的注意，但归根结底，化学多样性和有机体的适应新陈代谢创造了所有物种都利用来生存的“内源性药物”。该项目将产生信息，以更好地了解化学水平上正在进行的进化变化过程的分子基础。反过来，这些信息不仅为人类提供了在分子和代谢水平上对生物进化的了解，还为操纵这一框架提供了一个框架，用于创造新的化学物质，用于药物发现，改善营养，并最终实现更健康的生活。

Plant phenylpropanoids including flavonoids and stilbenes comprise a structurally diverse group of secondary metabolites that play vital roles in the interaction of plants with their surrounding environment. The utility of these compounds in plants varies widely and includes roles as structural polymers, defense barriers, defense chemicals synthesized in response to microbial, insect, and herbivore predation, signaling molecules for nitrogen-fixing rhizobia bacteria, UV-protective agents, and pigments. In addition to their role in plant physiology, phenylpropanoids possess a number of properties that have proven useful to the pharmaceutical, food, agricultural, and nutritional industries. A major goal of this project is to understand the molecular mechanisms underlying the biosynthesis of plant phenylpropanoids. The current objectives of this research are to examine the functional diversity of the chalcone synthase (CHS) / stilbene synthase (STS) superfamily of plant polyketide synthases involved in the initial stages of flavonoid biosynthesis using both x-ray crystallography and enzymological studies, the mechanism, stereochemistry, and selectivity of chalcone isomerase (CHI)-mediated flavanone formation in both chalcone and deoxychalcone biosynthetic pathways, the structure and mechanism of chalcone reductase (CHR), and the energetic and architectural features of multienzyme complex formation involving CHS, CHI, and/or CHR during flavonoid and isoflavonoid biosynthesis using surface plasmon resonance and TROSY-NMR. These studies will elucidate the mechanisms governing phenylpropanoid production in plants and in particularly will relate the biosynthetic diversity of these pathways to on-going evolutionary change that leads to this biologically important form of chemical diversity. Significantly, the broader impacts resulting from the proposed research activities include a significant training component that involves the exclusive participation of both graduate (PhD) and undergraduate (BS) students in groups under represented in scientific research. In addition, key scientific findings generated by this research will be disseminated to the public principally through annual lectures organized through an evening seminar series for the general public that discusses in lay terms the science and significance of the on-going publicly supported work at the Salk Institute. Recently, key findings obtained during the initial stages of this project described the benefits of understanding plant secondary metabolism for mankind with regard to agriculture, disease prevention, and drug discovery. A number of plant-derived phenylpropanoids are valuable medicinal agents. Moreover, the regular dietary consumption of phenylpropanoid-derived compounds including lignans, stilbenes, and (iso)flavonoids has considerable health benefits including lowered risk factors for both cancer and coronary artery disease. The enzyme scaffolds that are used by plants to create these small molecules serve as novel and useful starting points to create new molecular entities for drug discovery using a novel approach that includes structural biology and genomics. Most importantly, all organisms utilize chemical diversity to live and prosper in harsh and challenging environments. While an organism's protein and gene diversity have captured the public's attention over the last several years, ultimately, chemical diversity and an organism's adapting metabolism create "endogenous drugs" that all species exploit for survival. This project will generate information with which to better understand the molecular basis for this on-going process of evolutionary change at the chemical level. In turn, such information not only provides mankind with an understanding of organismal evolution at the molecular and metabolic level, but also provides a framework for manipulating this framework for the creation of new chemicals for drug discovery, improvements in nutrition, and ultimately, a healthier life.