CAS: Enzymatic Hydrolytic Dehalogenation of Chlorinated Aromatic Compounds

CAS：氯化芳香族化合物的酶水解脱卤

• 批准号: 2003861
• 负责人: Richard Holz
• 金额: $ 45万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-15 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2003861&HistoricalAwards=false
• 关键词: CAS; Enzymatic; Hydrolytic; Dehalogenation; Chlorinated

With this award, the Chemistry of Life Processes in the Chemistry Division is funding Dr. Holz from the Colorado School of Mines to investigate how the enzyme chlorothalonil dehalogenase (Chd) selectively converts under ambient conditions an aromatic carbon-chlorine (C-Cl) bond to an aromatic carbon-hydroxide (C-OH) bond on chlorothalonil (TPN; 2,4,5,6-tetrachloroisophthalonitrile). TPN is a fungicide that is widely used in the US; more than five million kilograms of TPN are sprayed every year on fruits and crops in the US. TPN is strongly absorbed in soil, particularly soil with high organic matter such as that found in aquatic environments, where it can remain and contaminate groundwater for years. TPN is highly toxic to fish and other aquatic species as well as to birds and invertebrates. TPN is also an irritant for human skin and eyes that can cause severe gastrointestinal issues and has been classified by the U.S. Environmental Protection Agency (EPA) as a probable human carcinogen. Chd is an important enzyme in the bioremediation of TPN and is thus becoming increasingly recognized as a new “Green” biocatalyst. Dr. Holz’s research will use an interdisciplinary experimental approach to gain insight into how TPN is hydrolyzed by Chd. Understanding the catalytic mechanism of Chd would provide insight into its bioremediation potential and potentially facilitate the expansion of this catalytic chemistry through biomimetic and protein engineering approaches. These research activities create a stimulating intellectual environment for the undergraduate and graduate students who implement the work. Dr. Holz also focuses on (i) broadening participation of students from backgrounds underrepresented in STEM careers via student recruitment, and (ii) increase undergraduate participation in research. Halogenated aromatic compounds are known to be major organic pollutants given their high toxicity and carcinogenic properties. These compounds enter the environment as contaminants derived from industrial processes where they are widely used as solvents, defatting agents, and fungicides. The removal of these compounds from the environment is challenging because of their chemical stability, resistance to degradation, and lipophilic properties. Use of an enzyme such as chlorothalonil dehalogenase in the bioremediation of environments contaminated with halogenated aromatic compounds is conditioned upon the understanding at molecular level of the mechanism of the Chd-catalyzed hydrolysis of TPN. The research supported by this award will focus on answers three specific questions about the Chd catalytic role: (i) What are the determinants of the recognition and binding of the halogenated aromatic reaction substrates to Chd?, (ii) Does substrate bind to the Zn(II) ions in the active site of the enzyme and what is the structure of the transition state?, and (iii) Which residues in the active site of Chd are important for the catalysis? Dr. Holz and his team will use a combination of protein biochemistry, spectroscopy and enzyme kinetic analysis, computational chemistry, and X-ray crystallographic studies. The successful completion of this project will enhance our understanding of the catalytic mechanism of Chd and stimulate development of engineered catalysts for deployment in synthesis, biocatalysis and bioremediation.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.

有了这个奖项，化学划分的生命过程的化学过程是为科罗拉多州矿业学院的Holz提供资金，以调查如何在环境条件下选择性转化芳族碳氯（C-CL）键在芳族碳氧化碳（C-C-hydroxion（C-C-oh）上，在环境条件下如何选择性地转换为Chydrosy（C-CL）键2,4,5,6-四氯二甲硝基苯二甲甲氟二氯）。 TPN是在美国广泛使用的杀菌剂。在美国，每年在水果和农作物上喷洒超过500万公斤的TPN。 TPN被强烈吸收在土壤中，尤其是具有高有机物的土壤，例如在水生环境中发现的土壤，它可以保留并污染地下水多年。 TPN也是对人皮肤和眼睛的刺激性，可能引起严重的胃肠道问题，并已被美国环境保护局（EPA）分类为有问题的人类致癌物。 CHD是TPN生物修复中的重要酶，因此被越来越被公认为是一种新的“绿色”生物催化剂。 Holz博士的研究将采用跨学科的实验方法来深入了解CHD如何水解TPN。了解冠心病的催化机制将提供对其生物修复潜力的见解，并有可能通过仿生和蛋白质工程方法来支持这种催化化学的扩展。这些研究活动为实施这项工作的本科生和研究生创造了刺激性的智力环境。 Holz博士还专注于（i）（i）通过学生招聘在STEM职业中的背景不足的学生的参与，以及（ii）增加本科参与研究的参与。鉴于其高毒性和致癌特性，已知卤化的芳族化合物是主要有机污染物。这些化合物作为污染物进入环境，这些污染物是从工业过程中得出的，它们被广泛用作解决方案，偏差剂和杀菌剂。由于它们的化学稳定性，对降解性和亲脂性特性，因此从环境中去除这些化合物是具有挑战性的。在用卤化芳族化合物污染的环境中使用诸如氯噻酮脱核酶的酶的使用基于对TPN的CHD催化水解的机制的理解。该奖项支持的研究将重点介绍有关CHD催化作用的三个特定问题：（i）确定卤化芳族反应底物与CHD的识别和结合？ Holz博士和他的团队将结合蛋白质生物化学，光谱和酶动力学分析，计算化学和X射线晶体学研究。该项目的成功完成将增强我们对CHD催化机制的理解，并刺激工程的发展。该奖项反映了NSF的法定任务，并通过基金会的知识分子优点和更广泛的影响评估标准来诚实地支持NSF的法定任务。