Discovery and Characterization of SAM-Dependent Pericyclases

大自然使用酶以高效率和高选择性加速化学反应。酶被用来制造复杂的物质，称为天然产物。 这些反应中的许多对化学界都很重要，并且有稳定的酶来执行它们可以导致更绿色的化学。 因此，对这些酶如何发挥作用的新认识对于化学工业的应用以及发现稳定和强大的新酶非常重要。 该奖项来自化学系生命过程化学项目，研究了洛杉矶的加州大学Yi Tang和Kendall Houk教授实验室最近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，因为它们可以在一个步骤中形成多个键。 然而，这种酶只有少数几个例子存在，并且与使用有机化合物可以做的事情相比，化学非常有限。 这组环化酶使用S-腺苷甲硫氨酸或SAM的伴侣来催化生物学中从未见过的一组转化。 该项目结合了多学科团队，使用生物化学，结构和计算方法研究这些酶。 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寻找更多的例子。 该项目还整合了一个外展计划，让当地高中生和本科生在我们的研究实验室进行指导研究，并向他们介绍酶的力量。 周环反应是区域选择性和立体选择性地制备多键的最有力的合成转化之一。这些反应已被广泛应用于含有连续立体碳中心的生物活性复杂天然产物的合成。尽管周环反应在全合成中的突出地位，然而，在过去的五十年中，只有有限的酶催化的周环反应的特点。 LepI代表了一个新的周环酶家族（催化周环反应的酶），其使用S-腺苷甲硫氨酸（SAM）催化生物学上前所未有的反应，包括异Diels桤木环化和[3，3]-sigmatropic retro-Claisen重排。 该项目的首要目标是了解LepI家族中的周环酶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周选择性（选择性形成一种周环反应产物）是如何控制的。 生物化学，结构和计算表征方法的组合被用来研究酶。 拟议的研究导致了新的见解，自然如何催化这些具有挑战性的反应和控制的区域和立体选择性，并将建立一个新的作用，SAM在酶催化。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的知识价值和更广泛的影响审查标准的支持。

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.