Collaborative Research: A Comprehensive Study of the Structure, Function, and Diversity of Detoxification Enzymes (CYP2B) in Mammalian Herbivores (Neotoma)

每顿饭，成千上万种食草哺乳动物都面临着被食物产生的天然毒素中毒的可能性。食草哺乳动物的普遍觅食习惯，每天吃许多不同种类的植物，被认为是由于它们的肝酶的限制。通才被认为具有“多面手”式的解毒系统，该系统由能够代谢多种植物毒素的肝酶组成，但催化效率较低。相比之下，专家被认为拥有对有限数量的毒素具有更高效率的解毒酶。这种关于饮食专业化的生化权衡的概念基本上已经成为教条，没有任何实验支持。这项研究将利用从模型物种和人类药物代谢研究中获得的哺乳动物解毒酶的广泛知识，以及哺乳动物食草动物最高级野生啮齿动物模型的可用性。长期目标是通过对草食性木鼠细胞色素P450亚家族2B （CYP2B）肝酶的重点研究，确定饮食暴露于植物毒素如何影响哺乳动物的解毒系统。本次合作研究的具体目标是：1)在氨基酸水平上表征木鼠CYP2B酶。2)。利用新的代谢组学方法鉴定木鼠日粮中关键的P450底物，并比较木鼠CYP2B酶对植物毒素的代谢。3)。利用定点诱变和x射线晶体学对木草CYP2B酶进行结构-功能分析。这项工作将通过利用尖端的生化和结构生物学方法来解决一个长期存在的假设，从而对野生食草动物的CYP2B酶进行首次详细检查，确定底物，并比较酶的功能。最终目的是解决木聚糖酶与植物毒素复合物的晶体结构。目前，对哺乳动物解毒酶的认识还很初级。鉴于这些研究人员对木聚糖酶的初步数据，这项工作有可能有助于了解人类药物代谢。此外，木鼠是大自然的历史学家；他们储存食物的行为促进了对过去35000年来西南沙漠发生的自然变化的理解。犹他州自然历史博物馆将举办一场关于木鼠生态及其对社会重要性的互动展览。pi将指导新一代的学员（从高中生到博士后）进行跨学科研究。该奖项由化学学部生命过程化学项目共同资助。

At every meal, thousands of species of plant-eating mammals confront the possibility of being poisoned by the natural toxins produced by their food. The generalized foraging habit of mammalian herbivores, eating many different plant species on a daily basis, is thought to result from limitations of their liver enzymes. Generalists are hypothesized to have a "jack of all trades" style of detoxification system that consists of liver enzymes able to metabolize a wide array of plant toxins but with low catalytic efficiency. In contrast, specialists are thought to have detoxification enzymes with enhanced efficiency towards a restricted number of toxins. This concept of biochemical tradeoffs with respect to dietary specialization has essentially become dogma without any experimental support. This research will capitalize on the extensive knowledge of mammalian detoxification enzymes gained from studies of drug metabolism in model species and humans, as well as on the availability of a superlative wild rodent model of mammalian herbivory. The long-term objective is to determine how dietary exposure to plant toxins has shaped the mammalian detoxification system through a focused study of liver enzymes in the cytochrome P450 subfamily 2B (CYP2B) in herbivorous woodrats (Neotoma). The specific goals of this collaborative research are: 1.) Characterize the CYP2B enzymes in woodrats at the amino acid level. 2.) Use new metabolomic approaches to identify key P450 substrates in diets of woodrats and compare metabolism of plant toxins by woodrat CYP2B enzymes. 3.) Conduct structure-function analyses using site-directed mutagenesis and X-ray crystallography of woodrat CYP2B enzymes. The work will address a longstanding hypothesis by drawing upon cutting-edge biochemical and structural biology approaches to generate the first detailed examination of CYP2B enzymes of wild herbivores, identify substrates, and compare enzyme function. The ultimate goal is to solve the crystal structures of woodrat enzymes in complex with plant toxins. Currently, knowledge of detoxification enzymes of mammals is rudimentary. The work has the potential to contribute to the understanding of drug metabolism in humans given preliminary data of these investigators on woodrat enzymes. In addition, woodrats are nature's historians; their behavior of storing food has facilitated an understanding of the natural changes that have taken place in the desert southwest over the last 35,000 years. An interactive display about the ecology of woodrats and their importance to society will be developed at the Utah Museum of Natural History. The PIs will mentor a new generation of trainees (high school students through postdoctoral fellows) in interdisciplinary research. This award is co-funded by the Chemistry of Life Processes Program in the Division of Chemistry.