Decreasing the oxygenase activity of Rubisco: a synthetic biology approach

降低 Rubisco 的加氧酶活性：一种合成生物学方法

基本信息

批准号：
BB/J004057/1
负责人：
Nicholas Smirnoff
金额：
$ 22.24万
依托单位：
UNIVERSITY OF EXETER
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FJ004057%2F1
关键词：
Decreasing oxygenase activity Rubisco synthetic

项目摘要

Photosynthesis is the process whereby plants convert atmospheric carbon dioxide to organic matter (biomass) using energy from sunlight. Photosynthesis powers plant growth, crop productivity and all life on earth. The first step in photosynthesis combines carbon dioxide with a sugar containing 5 carbon atoms to make two sugar molecules each containing 3 carbon (C3) atoms in a process called carbon dioxide fixation. The C3 sugars then combine to regenerate the 5 carbon accceptor and also to form glucose. Glucose is used as the feedstock to synthesise all other molecules in the plant. Chemical reactions in plants, such as the first step in photosynthesis, only happen quickly enough if they are speeded up by proteins known as enzymes. Rubisco is the enzyme that speeds up carbon dioxide fixation. Unfortunately this enzyme has built-in inefficiencies. It is slow, so plants need to spend energy producing it in large quantities. It also has a side reaction in which oxygen competes with carbon dioxide to react with the 5C acceptor. The consequence of this side reaction (known as the oxygenase reaction) is that less C3 product is formed and photosynthesis rate is slower than it could be. Some algae and plants have developed elaborate mechanisms to increase the concentration of carbon dioxide near Rubisco, thereby decreasing oxygenase activity and increasing the efficiency of photosynthesis. Unfortunately, many of our major crops (e.g. rice, wheat, potatoes and pulses) do not have this mechanism and various approaches to reducing their oxygenase activity are being intensively investigated. To contribute to this effort, we are proposing a pilot study to assess the potential of physically linking Rubisco to another enzyme (carbonic anhydrase, CA) which, under the right conditions, could deliver a high concentration of carbon dioxide to Rubisco and reduce the wasteful oxygenase activity. To achieve this aim we propose to reconfigure the carbon dioxide fixing step of photosynthesis by engineering the bacterium Synechocystis. We will prepare a synthetic gene which, when introduced into Synechocystis will cause it to produce a protein scaffold that can bind both Rubisco and CA. The modified strain will also contain forms of Rubisco and CA that have been engineered with tags that allow them to bind to the scaffold protein. This engineered organism will allow us to test the proposal that close proximity of Rubisco and CA increases the efficiency of photosynthesis by decreasing the "wasteful" oxygenase activity.

光合作用是植物利用阳光能量将大气中的二氧化碳转化为有机物（生物质）的过程。光合作用为植物生长、作物生产力和地球上的所有生命提供动力。光合作用的第一步是将二氧化碳与含有 5 个碳原子的糖结合，形成两个糖分子，每个糖分子含有 3 个碳 (C3) 原子，这一过程称为二氧化碳固定。然后 C3 糖结合再生 5 碳受体并形成葡萄糖。葡萄糖被用作合成植物中所有其他分子的原料。植物中的化学反应，例如光合作用的第一步，只有在被称为酶的蛋白质加速的情况下才能足够快地发生。 Rubisco 是一种加速二氧化碳固定的酶。不幸的是，这种酶具有固有的低效率。它的速度很慢，因此植物需要消耗能量来大量生产它。它还存在副反应，其中氧气与二氧化碳竞争与5C受体反应。这种副反应（称为加氧酶反应）的结果是形成较少的 C3 产物，并且光合作用速率低于其应有的速度。一些藻类和植物已经发展出复杂的机制来增加 Rubisco 附近的二氧化碳浓度，从而降低加氧酶活性并提高光合作用的效率。不幸的是，我们的许多主要作物（例如水稻、小麦、马铃薯和豆类）不具备这种机制，并且正在深入研究降低其加氧酶活性的各种方法。为了促进这一努力，我们提议开展一项试点研究，以评估将 Rubisco 与另一种酶（碳酸酐酶，CA）物理连接的潜力，在适当的条件下，该酶可以向 Rubisco 传递高浓度的二氧化碳，并减少浪费加氧酶活性。为了实现这一目标，我们建议通过改造集胞藻细菌来重新配置光合作用的二氧化碳固定步骤。我们将准备一个合成基因，当将其引入集胞藻时，将导致其产生可以结合 Rubisco 和 CA 的蛋白质支架。修饰后的菌株还将含有 Rubisco 和 CA 的形式，这些形式经过改造，带有标签，使它们能够与支架蛋白结合。这种工程有机体将使我们能够测试 Rubisco 和 CA 的紧密接近通过减少“浪费的”加氧酶活性来提高光合作用效率的提议。