The Influence of Primary Coordination Sphere in Aromatic C-C Ring Scission: Mechanistic Studies of 3-His Coordinated Non-heme Iron Enzymes

在化学学部生命过程化学（CLP）项目的支持下，纽约城市大学史坦顿岛学院的Rupal Gupta博士将研究铁酶对芳香有机分子的生物降解。导致这些化合物分解的化学反应的焦点是一个铁中心，这个铁中心通过在大多数铁酶中普遍存在的支架被拴在蛋白质上。然而，最近发现了几种新的铁结合支架。这些非典型结合位点对酶的反应性、效率和选择性的影响尚不清楚。拟议的研究将以系统的方式评估金属结合支架对酶功能的作用。这些研究的发现将为人工催化剂的设计提供信息，并为自然界进行的具有挑战性的化学反应提供见解。该项目还将有助于对本科生和高中生进行严格的培训，他们将通过外展项目了解生物化学、酶学和光谱学的概念，并将有机会进行基于课程的研究。催化无数化学反应的非血红素铁酶通常具有由两个组氨酸和一个羧酸残基（2- his -1-羧酸）组成的金属结合基序。近年来发现了几种非典型金属结合基序，如3-His、3-His-1-羧酸盐和4-His。这种初级配位球的变化明显改变了金属中心的配体场，预计会影响铁中心的催化作用。该项目的总体目标是系统地了解初级配位球对非血红素铁酶进行C-C环断裂的反应性和催化作用的影响。利用生物化学和光谱学相结合的方法，研究了3-His芳香环切割酶的反应机理，重点研究了初级配位球对反应动力学和反应中间体的电子和磁性质的影响。这些研究将有助于评估非典型金属结合基序的性质及其对反应性和底物选择性的影响。该奖项反映了美国国家科学基金会的法定使命，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。

With the support of the Chemistry of Life Processes (CLP) Program in the Chemistry Division, Dr. Rupal Gupta from the College of Staten Island, City University of New York will investigate the biological degradation of aromatic organic molecules by iron enzymes. The focal point of chemical reactions responsible for the decomposition of these compounds is an iron center that is tethered to the protein via a scaffold ubiquitously found in most iron enzymes. However, several novel iron-binding scaffolds have been recently identified. The influence of these atypical binding sites on enzymatic reactivity, efficiency and selectivity is not clear. The proposed studies will evaluate the role of metal binding scaffolds toward enzymatic function in a systematic manner. Findings from these studies will inform the design of artificial catalysts and offer insights into the challenging chemical reactions performed by Nature. This project will also contribute to the rigorous training of undergraduates and high school students, who will be introduced to concepts of biochemistry, enzymology and spectroscopy through outreach programs and will be offered opportunities to conduct curriculum-based research. Non-heme iron enzymes that catalyze a myriad of chemical reactions typically bear a metal-binding motif composed of two histidine and one carboxylate residues (2-His-1-carboxylate). Recently, several atypical metal binding motifs such as 3-His, 3-His-1-carboxylate and 4-His, have been identified. Such variations in the primary coordination sphere that clearly alter the ligand field at the metal center are expected to influence the catalysis carried out by the iron center. The overall goal of this project is to gain a systematic understanding of the influence of the primary coordination sphere on the reactivity and catalysis of non-heme iron enzymes performing C-C ring scission. By utilizing a combination of biochemical and spectroscopic methodologies, reaction mechanisms of 3-His aromatic ring cleaving enzymes will be investigated with a focus on identifying the influence of the primary coordination sphere on reaction kinetics and, electronic and magnetic properties of the reaction intermediates. These studies will help evaluate the properties of atypical metal binding motifs and their impact on the reactivity and substrate selectivity.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.