Mechanistic Studies on Fe-Type Nitrile Hydration Catalysts

该奖项由化学部生命过程化学研究所颁发，资助马奎特大学的Bennett和Holz博士研究在环境条件下，腈水合酶(NHase)如何将称为腈的化学基团转化为酰胺。有趣的是，氨酶不仅可以水合生物体系中的腈，还可以水合广泛的合成腈。因此，氨酶被广泛应用于制备有机化学实验室以及丙烯酰胺和烟酰胺的工业生产。氨酶还被证明在清除环境中的氰基化学品和杀虫剂方面很有用，因此越来越多地被认为是一种新型的“绿色”催化剂。对强调其化学反应性和应用的机理的了解可以为开发新的生物催化剂提供动力。贝内特博士和霍尔茨博士的研究使用跨学科的实验方法来深入了解氨酶是如何使氰化物水合的。他们的研究和教育努力有助于促进研究生和本科生的教学、培训和学习，特别是那些来自代表性不足群体的学生。他们的研究还加强了马奎特大学的研究和教育基础设施。虽然氨酶的生物学作用还不是很清楚，但它们可能包括营养代谢、丁腈解毒和/或营养同化。氰化物在生物系统中最常见，如氰糖苷或氰脂，但许多植物也会产生氰化物，如蓖麻毒素和β-氰基丙氨酸，用于自卫。理解它们的生物和生物修复作用的主要障碍是缺乏对它们的催化机制的了解。Bennett博士和Holz博士结合了动力学、光谱、生物化学、计算化学和X射线结晶学研究，在分子水平上深入了解了NHase对腈的水合作用。三个具体问题的答案被寻求：(1)丁腈水合的过渡态是什么？(2)催化所需的磺酸环中间体和轴向α-半胱氨酸配体之间是否存在瞬时的二硫键？以及(3)是什么控制了Fe型NHase中金属分配中心的组装？该项目的成功完成加深了我们对NHASS催化机理的了解，并促进了工程化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。

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.