Mechanism of Substrate Transformations by the Complex Iron Sulfur Molybdoenzyme (CISM) Family

该奖项由化学部生命过程化学项目资助印第安纳大学-普渡大学印第安纳波利斯分校的Partha Basu博士研究复杂的铁硫钼酶(CISM)呼吸酶家族如何催化多种化学物质的还原。呼吸作用是所有生命系统中产生能量的基本新陈代谢过程。许多微生物利用特殊的酶进行厌氧呼吸，其中硝酸盐、高氯酸盐和二甲基亚砜等底物被还原。这些代谢过程有助于生态多样性。使用生化、光谱、计算和动力学方法系统地研究了这些CISM酶的活性部位的结构如何使它们显示底物选择性。这个项目为研究生和博士后研究员提供专门的酶学、光谱学和计算方面的培训。此外，这项研究还被整合到一个推广计划中，向高中生介绍酶的研究，并吸引没有攻读理科学位的一年级学生进入理科。该项目的一个重点是利用研究向STEM职业生涯中代表性较低的群体的学生传达对科学的欣赏。CISM酶是一种普遍存在的酶，在转化不同的氧阴离子过程中起着重要的生理作用。本研究项目以周质硝酸还原酶为模型酶，开发了该酶的几个突变体，系统地改变了钼的配位环境。酶变异体的动力学分析有助于建立底物选择性的定量图景。此外，催化口袋中的几个残基被鉴定为参与质子穿梭和底物结合。这些残基的突变提供了关于反应机制的有价值的信息。动力学数据放在酶的结构和光谱性质的背景下。这项拟议的研究提供了对由CISM家族成员催化的底物转变的新的详细见解。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。

With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Partha Basu of Indiana University–Purdue University Indianapolis to investigate how the Complex Iron-Sulfur Molybdoenzyme (CISM) family of respiratory enzymes catalyze the reduction of a wide variety of chemicals. Respiration is an essential metabolic process that generates energy in all living systems. Many microorganisms utilize specialized enzymes to carry out anaerobic respiration where substrates such as nitrate, perchlorate, and dimethyl sulfoxide are reduced. These metabolic processes contribute to ecological diversity. Biochemical, spectroscopic, computational, and kinetic methods are used to systematically study how the structure of the active site of these CISM enzymes allows them to display substrate selectivity. This project provides graduate students and postdoctoral fellows with specialized training in enzymology, spectroscopy, and computation. In addition, the research is integrated into an outreach program that introduces high school students to the study of enzymes and attracts first-year students who are not pursuing a science degree to science. A strong emphasis of the program is to use research to convey to students from groups underrepresented in STEM careers an appreciation for science. CISM enzymes are ubiquitous and play essential physiological roles in transforming different oxyanions. This research project uses periplasmic nitrate reductase as a model enzyme and develops several mutational variants of this enzyme where the coordination environment of molybdenum is systematically modified. The kinetic analyses of the enzyme variants help develop a quantitative picture for substrate selectivity. In addition, several residues in the catalytic pocket are identified as being involved in proton shuttling and substrate binding. Mutations of these residues provide valuable information about the mechanism of the reaction. The kinetic data are placed in the context of structural and spectroscopic properties of the enzyme. The proposed research provides new detailed insights into the substrate transformations catalyzed by members of the CISM family.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.