Discovery and Characterization of SAM-Dependent Pericyclases

自然界使用酶来高效和选择性地加速化学作用。酶被用来制造被称为天然产品的复杂材料。其中许多反应对化学界都很重要，有稳定的酶来进行这些反应可以带来更绿色的化学。因此，对这些酶的功能有了新的了解，对于化学工业中的应用以及发现稳定和强大的新酶都很重要。该奖项由化学部生命过程化学计划颁发，旨在研究最近在加州大学洛杉矶分校唐毅教授和Kendall Houk教授的实验室中发现的一类新酶的基本性质：一组催化周环反应的酶。周环反应在合成化学中非常重要，因为它们可以在一步中形成多个键。然而，这种酶的例子很少，而且与使用有机化合物所能完成的相比，化学作用非常有限。这组周环蛋白使用一个伙伴，S-腺苷甲硫氨酸，或SAM，催化一系列在生物学中前所未见的转化。这个项目结合了一个多学科的团队，使用生化、结构和计算方法来研究这些酶。这项工作的结果可以阐明催化的潜在基础，并使我们能够通过其他微生物搜索更多的例子。该项目还整合了一个外展计划，让我们研究实验室的当地高中生和本科生参与指导研究，并向他们介绍酶的力量。周环反应是具有区域选择性和立体选择性的多键合成反应中最有效的一种。这些反应已被广泛应用于合成具有生物活性的含连续立体生碳中心的复杂天然产物。然而，尽管周环反应在全合成中占有重要地位，但在过去的五十年里，只有有限的酶催化的周环反应得到了表征。LepI代表了一个新的周环酶家族，它使用S-腺苷甲硫氨酸(SAM)催化生物上前所未有的反应，包括杂Diels Alder环化和[3，3]-Sigmatrotic逆克莱森重排。这个项目的主要目标是了解LepI家族中周环类化合物催化反应的结构和机理基础，特别是SAM在催化中的作用以及如何控制周环反应产物的选择性形成。目前正在使用生化、结构和计算表征方法相结合的方法研究该酶。拟议的研究正在引导人们对自然如何催化这些具有挑战性的反应并控制区域和立体选择性的新见解，并将为SAM在酶催化方面建立一个新的角色。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nature uses enzymes to accelerate chemistry with high efficiency and selectivity. Enzymes are employed in making complex materials known as natural products. Many of these reactions are of importance to the chemical community, and having stable enzymes to carry them out can lead to greener chemistry. Gaining new understandings of how these enzymes function is therefore important towards applications in the chemical industry, as well as discovering new enzymes that are stable and powerful. This award from the Chemistry of Life Processes Program in the Chemistry Division examines the underlying properties of a new class of enzymes discovered recently in the laboratories of Professors Yi Tang and Kendall Houk at the University of California at Los Angeles: a set of enzymes that catalyze pericyclic reactions. Pericyclic reactions are immensely important in synthetic chemistry, as they can lead to the formation of multiple bonds in a single step. However, only a few examples of such enzymes exist and the chemistry is very limited compared to what can be done using organic compounds. This set of pericyclases uses a partner, S-adenosylmethionine or SAM, to catalyze a set of transformations never before seen in biology. This propject combines a multidisciplinary team to study these enzymes using biochemical, structural and computation methods. Results from this work can illuminate the underlying basis of catalysis, and enables us to search through other microbes for additional examples. The project also integrates an outreach program that involves local high school students and undergraduate students in our research laboratories to perform mentored research, and introduces them to the power of enzymes. Pericyclic reactions are among the most powerful synthetic transformations to make multiple bonds regioselectively and stereoselectively. These reactions have been widely applied for the synthesis of biologically active complex natural products containing contiguous stereogenic carbon centers. Despite the prominence of pericyclic reactions in total synthesis, however, only limited enzyme catalyzed pericyclic reactions have been characterized over the past five decades. LepI represents a new family of pericyclases (enzymes that catalyze a pericyclic reaction) that use S-adenosylmethionine (SAM) to catalyze biologically unprecedented reactions, including hetero-Diels Alder cyclization and a [3,3]-sigmatropic retro-Claisen rearrangement. The overarching goal of this project is to understand the structural and mechanistic basis of the reactions catalyzed by pericyclases in the LepI family, especially the role of SAM in catalysis and how periselectivity (selective formation of one pericyclic reaction product) is controlled. A combination of biochemical, structural and computational characterization methods are being used to study the enzyme. The proposed studies are leading to new insights into how nature catalyzes these challenging reactions and controls the regio- and stereoselectivity, and will establish a new role for SAM in enzyme catalysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.