Chemistry without Cofactors: Discovering How a Protein Environment Facilitates Important Reactions with Oxygen

细胞对食物的代谢在我们的细胞内经过一系列漫长而复杂的步骤，本质上类似于被称为燃烧的化学反应，即碳化合物与氧气（O2）结合，产生二氧化碳、水和大量能量。隐藏在蛋白质内部的“燧石”由一种叫做辅因子的小的含金属或类似维生素的化合物组成，这种化合物与氧分子结合，并开始破坏其化学键。然后，部分分解的氧分子准备与食物中的含碳分子结合，释放出大量的能量。通过这种方式，辅因子允许大自然利用和控制大气中氧气的力量。这个项目的主要目的是研究这个过程中令人惊讶的变化。最近发现的蛋白质在没有辅因子的帮助下催化含碳分子和氧之间的反应。这个项目研究这些蛋白质如何有效地产生“无火石的火”或没有辅助因子的能量。该项目还研究了这些蛋白质的重要潜在生物技术应用。无辅助因子、基于蛋白质的催化剂可以很容易地在细菌培养物中生长，而不需要昂贵的添加成分或将辅助因子组装成蛋白质所需的复杂生化途径。此外，这些生物催化剂为进行类似过程的现有化学方法提供了清洁、无副产品的替代品。该项目专门研究了无辅助因子蛋白如何有效地将丰富的可再生植物聚合物木质素转化为生产生物塑料的原料。该项目将培训从幼儿园到8年级的教师，并帮助开发一门关于可持续发展和科学教育问题的课程。研究生和本科生的研究培训和教育也将得到本项目的支持。O2是一种理想的氧化剂，因为它具有热动力、丰富度和副产品的良性性质。然而，O2具有不成对的电子自旋，这使得O2和有机分子之间的反应非常缓慢，除非有催化剂存在。与O2反应的生物催化通常依赖于辅因子。对辅助因子介导O2生物催化的要求通常被认为是绝对的。然而，最近发现了在完全没有辅助因子的情况下催化O2和有机物种之间多种反应的细菌酶。该项目的主要目标是确定单独的蛋白质环境如何激活O2并引导被激活的物种形成特定的产物，该项目专注于一个大家族的辅助因子独立酶。这个目标将实验与几个层次的理论结合起来。本项目由生物科学理事会分子与细胞生物科学部分子生物物理集群和数学与物理科学理事会化学部生命过程化学项目共同支持。

Metabolism of food by cells occurs over a long and elaborate series of steps inside our cells, which is, in essence, similar to the chemical reaction known as combustion, in which the carbon compounds combine with oxygen gas (O2), to yield carbon dioxide, water, and large amounts of energy. The "flint", hidden inside proteins, consists of small metal-containing or vitamin-like compounds called cofactors, which bind the O2 molecule and begin to break apart its chemical bonds. The partially dismantled oxygen molecule is then ready to combine with carbon-containing molecules from food, releasing vast amounts of energy. In this way, cofactors allow nature to harness and control the power of atmospheric O2. The main objective of this project is to investigate a surprising variation on this process. Recently discovered proteins catalyze reactions between carbon-containing molecules and O2 without the help of cofactors. This project examines how these proteins effectively generate "fire without flint" or energy without cofactors. This project also examines an important potential biotechnological application of these proteins. A cofactor-free, protein-based catalyst can be easily grown in bacterial cultures without the need for the expensive added ingredients or elaborate biochemical pathways needed for assembling cofactors into proteins. These biocatalysts moreover offer clean, byproduct-free alternatives to existing chemical methods for carrying out similar processes. This project specifically examines how cofactor-free proteins can efficiently convert the abundant, renewable plant polymer known as lignin into starting materials for the production of bioplastics. This project will train K through 8 teachers and help develop a course about teaching teachers on issues of sustainability and science education. Research training and education of graduate and undergraduate students will also be supported by this project.O2 is an ideal oxidant because of its thermodynamic power, abundance, and the benign nature of its by-products. However, O2 possesses unpaired electron spins, making reactions between O2 and organic molecules impractically slow unless a catalyst is present. Biological catalysis of reactions with O2 generally depends on cofactors. The requirement for cofactors to mediate O2 biocatalysis is generally considered absolute. However, bacterial enzymes that catalyze diverse reactions between O2 and organic species in the complete absence of cofactors have recently been discovered. The main objective for this project, which focuses on a large family of cofactor-independent enzymes, is to determine how the protein environment alone activates O2 and steers the activated species toward the formation of specific products. This objective integrates experiment with several levels of theory. This project is supported jointly by the Molecular Biophysics Cluster of the Molecular and Cellular Biosciences Division in the Directorate for Biological Sciences and Chemistry for Life Processes Program of the Chemistry Division in the Directorate of Mathematical and Physical Sciences.