Unraveling the principles of catalytic diversity in the carotenoid oxygenase superfamily

在化学部生命过程化学项目的支持下，加州大学欧文分校的Philip Kiser博士正在研究一种被称为类胡萝卜素裂解双加氧酶(CCDs)的酶家族。这些酶有一个高度保守的4-His铁中心，并显示出一系列非常不同的催化活性。众所周知，它们能氧化分解类胡萝卜素，类胡萝卜素是自然界中大量存在的有色化合物，包括许多食物中。除了这种氧化反应外，某些CCDs还催化涉及类胡萝卜素及其衍生物和非类胡萝卜素分子的其他反应。这些反应涉及几个重要的生物学过程，包括产生通用的光敏分子，分解废弃的植物物质，以及产生对动植物生理学至关重要的信号分子。因此，CCD功能的控制在农业、园艺、医药和生物燃料生产等各种应用研究领域一直是人们感兴趣的问题。尽管ccd很重要，但关于ccd如何实现如此多样化的活动，仍然存在许多关键的知识空白，因此限制了我们控制或修改其功能的能力。这一研究项目旨在提供分子水平的了解如何实现其不同的活动。这一新知识可能为利用小分子调节剂或通过合理改变其分子结构来控制ccd活性开辟新的途径。来自少数族裔群体和服兵役的研究生和本科生参与这项研究将有助于实现更广泛的教育目标，促进这些人进入STEM领域。本研究项目的主要重点是阐明CCDS所展示的各种活动的决定因素。第一个目标是利用各种复杂的光谱技术来揭示ccd触发氧气反应的机制。第二个目标将使用高分辨率X射线结晶学来揭示活性中心的性质，这些性质允许某些CCDs进行类胡萝卜素底物的反式顺式异构化。第三个目的是通过合理的诱变以及在占据不同生态位的古菌中发现的CD活性，来探索CD底物专一性的广度和机制。总体而言，这项研究将促进对ccd催化多样性的理解，并将为其进化和生物学功能提供新的见解。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 the support of the Chemistry of Life Processes Program in the Division of Chemistry, Dr. Philip Kiser from the University of California, Irvine is studying a family of enzymes known as carotenoid cleavage dioxygenases (CCDs). These enzymes have a highly conserved 4-His iron center and exhibit a remarkably diverse set of catalytic activities. They are well known to oxidatively split carotenoids, which are colored compounds found abundantly in nature including in many foods. Beyond this oxidation reaction, certain CCDs catalyze other reactions involving carotenoids and their derivatives and also non-carotenoid molecules. These reactions are involved in several important biological processes including the production of universal light-sensing molecules, breakdown of spent plant matter, and generation of signaling molecules critical for plant and animal physiology. As such, control of CCD function has long been of interest in a variety of applied research fields including agriculture, horticulture, medicine, and biofuel production. Despite their importance, many critical gaps in knowledge remain regarding how CCDs achieve such varied activities, which consequently has limited our ability to control or modify their function. This research project seeks to provide a molecular level understanding of how CCDs achieve their diverse activities. The new knowledge may open new avenues for controlling the CCD activity using small molecule modulators or by rational alteration of their molecular structure. The participation of graduate and undergraduate students from underrepresented minority groups and those with military service in this research will help achieve a broader educational goal of promoting the entry of such individuals into STEM-fields.The primary focus of this research project is to elucidate the determinants of the varied activities that are exhibited by CCDs. The first aim is to uncover the mechanism by which CCDs trigger dioxygen reactivity using a variety of sophisticated spectroscopic techniques. The second aim will employ high-resolution X-ray crystallography to uncover the active site properties that allow certain CCDs to carry out trans-cis isomerization of carotenoid substrates. The third aim focuses on probing the breadth and mechanism of CCD substrate specificity by rational mutagenesis and the CCD activities found in archaea that occupy diverse ecological niches. Overall, this research will advance the understanding of the catalytic diversity of CCDs and will provide novel insights into their evolution and biological functions.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.