Structural and Mechanistic Study of Mammalian Thiol Dioxygenases

该奖项由化学部的生命过程化学项目资助德克萨斯大学圣安东尼奥分校的刘爱民博士研究与硫磺氧化代谢相关的两种人类酶的结构和机制。两种重要的酶，半胱氨酸双加氧酶和半胱胺双加氧酶，负责激活氧气来处理有机硫醇部分。这两种酶的活性对控制代谢半胱氨酸和牛磺酸的浓度是必不可少的，它与自身免疫和神经状况、细胞信号、能量平衡和脂肪代谢有关。综合培训纳入研究项目，为学生提供全面和动手学习生化和结构生物学技术的机会。将制作电子顺磁共振光谱学的多媒体演示文稿，并用来向学生提供一个有形的演示，说明这种先进的光谱学如何澄清关键生物分子系统的化学性质。这项研究项目试图揭示在富含电子的硫中添加氧原子的机理以及蛋白质来源的辅因子的催化作用的性质。硫醇双加氧酶利用单核铁中心来促进分子氧结合到它们各自底物的硫醇部分中。这些酶在双加氧酶中是独一无二的，因为它们将分子氧的两个氧原子添加到一个底物原子上。虽然其他双加氧酶已经得到了很好的研究，但硫醇双加氧酶有望通过一种尚未很好建立的独特机制进行。刘博士正在研究这些酶的催化集合的形成，即依赖铁和氧的过程，以产生一种被称为蛋白质衍生辅因子的催化放大因子。包括蛋白质工程、EPR光谱、停流快速动力学和蛋白质X射线结晶学在内的一系列技术被用于确定辅因子生物发生和硫氧化的化学步骤。该项目的完成预计将揭示在一个富含电子的硫中添加两个氧原子的新机制含义，以及蛋白质衍生辅因子对硫代谢的催化贡献的性质。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. Aimin Liu from The University of Texas at San Antonio to investigate the structure and mechanism of two human enzymes involved in the oxidative sulfur metabolism. The two enzymes of interest, cysteine dioxygenase and cysteamine dioxygenase, are responsible for activating oxygen to process organic thiol moieties. The activity of these two enzymes is essential to manage metabolic cysteine and taurine concentrations and it is associated with autoimmune and neurological conditions, cellular signaling, energy balance, and fat metabolism. Integrated training is incorporated in the research project, which provides to students comprehensive and hands-on learning opportunities in biochemical and structural biology techniques. A multimedia presentation on electron paramagnetic resonance spectroscopy will be created and used to provide to students a tangible demonstration of how this advanced spectroscopy can clarify chemical properties of critical biomolecular systems. This research project seeks to reveal the mechanistic implications of adding oxygen atoms to electron-rich sulfur as well as the nature of the catalytic contribution of a protein-derived cofactor. The thiol dioxygenases utilize a mononuclear ferrous center to facilitate the incorporation of molecular oxygen into the thiol moiety of their respective substrates. These enzymes stand out as unique among dioxygenases because they add two of the oxygen atoms of molecular oxygen to a single substrate atom. Though other dioxygenases have been well studied, thiol dioxygenation is expected to proceed via a distinct mechanism that has not been well established yet. Dr. Liu is investigating the formation of the catalytic ensemble of these enzymes, namely an iron- and oxygen-dependent process for generating a catalytic amplifier known as the protein-derived cofactor. A wide array of techniques, including protein engineering, EPR spectroscopy, stopped-flow rapid kinetics, and protein X-ray crystallography, are employed in the determination of the chemical steps of cofactor biogenesis and sulfur oxygenation. The completion of this project is expected to reveal new mechanistic implications of adding two oxygen atoms to one electron-rich sulfur as well as the nature of the catalytic contribution of the protein-derived cofactor to sulfur metabolism.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.