Spectroscopic Studies of Molybdenum and Tungsten Enzymes

过渡金属离子是大量酶和其他蛋白质所必需的，其中过渡金属蛋白约占典型生物体基因组产量的11%。过渡金属离子被酶用来催化许多最具化学挑战性和与工业相关的反应，这些反应是由活的有机体进行的。在生物使用的所有过渡金属中，钼和钨被认为是唯一在生命中具有已知功能的第二排和第三排过渡元素。钨被进一步区分为已知的在生物学中具有功能作用的最重元素。钼和钨酶的结构非常密切，都含有一种不寻常的含硫有机辅因子，称为钼多蝶呤。 钼和钨在金属酶中的作用似乎经常是可以互换的，钼酶在高等生物中广泛存在，而钼的作用在更原始的生物中被钨所填补。总而言之，钼和钨的酶在几乎所有活着的有机体中都扮演着重要的角色，从古生物到细菌，再到植物和无脊椎动物。它们在酶活性部位做到这一点，这些酶活性部位虽然有共同的结构基序，如钼蝶呤，但在不同的化学反应被催化的范围内是显著的。这些酶发挥的功能也是多种多样的；例如，它们在微生物呼吸、绿色植物的氮素吸收、控制昆虫眼睛颜色和人类健康方面发挥着至关重要的作用。钨酶被认为在地球上的早期生命中发挥了重要作用，最显著的是在被称为Luca(最后一个全球共同祖先)的有机体中，有时被称为cen祖先，现在所有现存地球生命的祖先。 这项拟议的工作是使用同步加速器和计算化学方法相结合的方法对钼和钨酶的主要家族进行的系统研究。我们建议进一步发展一种新的整体方法，将X射线吸收光谱、先进的计算机分子模拟和晶体结构的信息结合起来，以获得迄今最准确的活性中心图像，从而阐明其详细的催化机理。因此，这项工作的最终目标是对酶使用的催化机制进行深入的量化、结构和电子理解，比较不同家族之间和内部的差异。这将导致对钼和钨酶如何实现其非凡的功能多样性的更丰富的理解。这项研究的好处有四个方面：(I)结果将为一组重要的酶产生详细的见解。(2)整体方法和为此制定的方法将广泛适用于任何金属蛋白的研究。(Iii)这些结果将提供对一组在地球原始生命中起重要作用的酶的见解。(Iv)通过推动和开发加拿大光源的技术，这项研究将加强加拿大研究人员在结构分子生物学中利用这些同步加速器工具的机会。

Transition metal ions are integral to a large number of enzymes and other proteins, with transition metalloproteins constituting about 11% of a typical organism’s genomic output. Transition metal ions are used by the enzymes to catalyze many of the most chemically challenging and industrially relevant reactions carried out by living organisms. Among all of the transition metals employed by living things, molybdenum and tungsten are distinguished as being the only second-row and third-row transition elements with a known function in life. Tungsten is further distinguished as the heaviest element known to have functional roles in biology. The structures of molybdenum and tungsten enzymes are very closely related, both containing an unusual sulfur-containing organic cofactor called molybdopterin. The roles of molybdenum and tungsten in metalloenzymes often appear to be interchangeable, with molybdenum enzymes found broadly in higher organisms, while the role of molybdenum is filled by tungsten in more primitive organisms. Together, the molybdenum and tungsten enzymes have important roles in almost all living organisms, from archaea to bacteria through plants to invertebrates and mammals. They do this within enzyme active sites that, while sharing common structural motifs such as the molybdopterin, are remarkable in the range of different chemical reactions are catalyzed. The functional roles fulfilled by the enzymes are equally diverse; for example, they play essential roles in microbial respiration, in the uptake of nitrogen in green plants, in controlling insect eye color, and in human health. The tungsten enzymes are thought to have played important roles in early life on earth, most notably in the organism known as the LUCA (last universal common ancestor), sometimes called the cenancestor, the progenitor of all earthly life now extant. The proposed work is a systematic study of the major families of molybdenum and tungsten enzymes using a combination of synchrotron-based and computational chemistry methods. We propose to further develop a novel holistic approach in combining information from X-ray absorption spectroscopy, advanced computer molecular modeling, and crystal structures to obtain the most accurate picture yet of the active sites, and thereby to elucidate their detailed catalytic mechanisms. The ultimate goal of the work is thus to develop an in-depth quantitative structural and electronic understanding of the catalytic mechanisms used by the enzymes, comparing and contrasting between and within the different families. This will lead to a richer understanding of how molybdenum and tungsten enzymes achieve their remarkable functional diversity. The benefits of this research are four-fold: (i) The results will yield detailed insights for an important group of enzymes. (ii) The holistic approach and the methods developed for it will be broadly applicable to studies of any metalloprotein. (iii) The results will provide insights into a group of enzymes that were important in primordial life on earth. (iv) By driving and developing techniques at the Canadian Light Source, the research will strengthen the opportunity for Canadian researchers to utilize these synchrotron tools in structural molecular biology.