Mechanistic Studies on Fe-Type Nitrile Hydration Catalysts

该奖项由化学部的生命过程化学颁发，资助马奎特大学的班尼特和霍尔茨博士研究腈水合酶（NHase）如何在环境条件下将称为腈的化学基团转化为酰胺。 有趣的是，NHases不仅可以水合生物系统中发现的腈，还可以水合各种合成腈。 因此，NHases广泛用于制备有机化学实验室和丙烯酰胺和烟酰胺的工业生产中。 NHases还被证明可用于从环境中清除腈基化学品和农药，因此越来越被认为是一种新型的“绿色”催化剂。 强调其化学反应性和应用的机制的知识可以为开发新的生物催化剂提供动力。 班尼特和霍尔茨博士的研究使用跨学科的实验方法来深入了解腈是如何被腈水合的。 他们的研究和教育工作有助于促进研究生和本科生的教学，培训和学习，特别是那些代表性不足的群体。 他们的研究还增强了马奎特大学的研究和教育基础设施。 虽然腈水解酶的生物学作用还不清楚，但它们可能包括营养代谢、腈解毒和/或营养同化。 腈在生物系统中最常见的形式是氰基糖苷或氰基脂，但许多植物也会产生腈，如蓖麻毒素和β-氰基丙氨酸用于自卫目的。 了解其生物和生物修复作用的主要障碍是缺乏对其催化机制的了解。 班尼特博士和霍尔茨博士结合动力学、光谱学、生物化学、计算化学和X射线晶体学研究，从分子水平上深入了解腈类化合物的水合作用。 本文试图回答三个具体问题：（1）腈水合的过渡态是什么？(2)次磺酸环状中间体和轴向α-Cys配体之间的瞬时二硫键是催化所需的吗？（3）Fe型NHAS中控制中心装配的因素是什么？ 该项目的成功完成增强了我们对NHases催化机制的理解，并刺激了工程生物修复催化剂的开发。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award by the Chemistry of Life Processes in the Chemistry Division, is funding Drs. Bennett and Holz from Marquette University to investigate how the enzyme Nitrile hydratase (NHase) transforms chemical groups called nitriles into amides under ambient conditions. Interestingly, NHases can hydrate not only nitriles found in biological systems but also a wide range of synthetic nitriles. Hence NHases are extensively used in preparative organic chemistry laboratories and in the industrial production of acrylamide and nicotinamide. NHases have also proven useful in the cleanup of nitrile-based chemicals and pesticides from the environment and are thus becoming increasingly recognized as a new type of "Green" catalyst. Knowledge of the mechanisms that underscore their chemical reactivity and applications could provide an impetus for the development of new biocatalysts. Drs. Bennett and Holz's research use an interdisciplinary experimental approach to gain insight into how nitriles are hydrated by NHases. Their research and education efforts help promote teaching, training and learning for graduate and undergraduate students, particularly those from underrepresented groups. Their research also enhances the infrastructure for research and education at Marquette University. While the biological roles of NHases are not well understood, they likely include nutrient metabolism, nitrile detoxification and/or nutrient assimilation. Nitriles are most commonly found in biological systems as cyanoglycosides or cyanolipids, but many plants also produce nitriles such as ricin and beta-cyanoalanine for self-defense purposes. The major impediment to understanding their biological and bioremediation roles is the lack of understanding of their catalytic mechanism. Drs. Bennett and Holz provide molecular level insight into the hydration of nitriles by NHases using a combination of kinetics, spectroscopy, biochemistry, computational chemistry, and X-ray crystallography studies. Answers to three specific questions are sought: (1) What is the transition-state of nitrile hydration? (2) Is a transient disulfide bond between the sulfenic acid cyclic intermediate and the axial alpha-Cys ligand required for catalysis? and (3) What controls metallocenter assembly in Fe-type NHases? Successful completion of this project enhances our understanding of the catalytic mechanism of NHases and stimulate development of engineered bioremediation catalysts.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.