Unraveling the principles of catalytic diversity in the carotenoid oxygenase superfamily

在化学系生命过程化学项目的支持下，来自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（CCD）的酶家族。这些酶具有高度保守的4-His铁中心，并表现出一系列非常多样化的催化活性。众所周知，它们可以氧化分解类胡萝卜素，类胡萝卜素是在自然界中大量存在的有色化合物，包括许多食物。除了这种氧化反应之外，某些CCD还催化涉及类胡萝卜素及其衍生物以及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过程，包括通用光敏分子的产生，废弃植物物质的分解，以及对植物和动物生理学至关重要的信号分子的产生。因此，CCD功能的控制长期以来在包括农业、园艺、医学和生物燃料生产的各种应用研究领域中一直受到关注。尽管它们很重要，但关于CCD如何实现这些不同的活动，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。该研究项目旨在提供对CCD如何实现其不同活动的分子水平的理解。新的知识可能会打开新的途径，控制CCD活动，使用小分子调制器或通过合理改变其分子结构。研究生和本科生的参与，从代表性不足的少数群体和那些在军队服役将有助于实现一个更广泛的教育目标，促进这些人进入STEM领域。本研究项目的主要重点是阐明的决定因素，表现出的各种活动的CCD。第一个目的是揭示CCD触发分子氧反应的机制，使用各种复杂的光谱技术。第二个目标将采用高分辨率X射线晶体学来揭示活性位点的性质，允许某些CCD进行类胡萝卜素底物的顺反异构化。第三个目标是探讨CCD底物特异性的广度和机制，通过合理的诱变和CCD活动中发现的古菌占据不同的生态位。总的来说，这项研究将促进对CCD催化多样性的理解，并将为它们的进化和生物功能提供新的见解。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.