Characterization of the Cyanide-resistant Oxidase in Plant Mitochondria

植物线粒体中抗氰氧化酶的表征

• 批准号: 9019735
• 负责人: James Siedow
• 金额: $ 20万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-07-01 至 1994-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9019735&HistoricalAwards=false
• 关键词: Characterization; Cyanide; resistant; Oxidase; Plant

The research outlined in this proposal is designed to continue the purification and characterization of the cyanide-resistant, "alternative" oxidase associated with the electron transfer chain of mitochondria in most plants, many fungi and some protozoa. The role of this energetically wasteful oxidase in plant energy metabolism is not known and only recently has progress been made identifying protein species associated with the oxidase. The PI has successfully carried out a partial purification of the alternative oxidase from the highly cyanide-resistant spadices of flowering skunk cabbage. This preparation will be further purified and the cofactors associated with the oxygen reduction reaction catalyzed by the enzyme will be identified. More specifically, the nature and amount of an auto-oxidizable quinone found to be associated with the enzyme will be determined as will the nature of any metals bound to the purified enzyme. Studies will also be carried out to determine the relative contributions of steric factors, redox potentials and quinone lipophilicity to the ability of a given quinone species to serve as an electron donor to the alternative oxidase. These studies will lead to a better under understanding of this unusual oxidase and the nature of its interaction with the mitochondrial electron transfer chain. Unlike animals, such as humans, plants have two respiratory pathways in their mitochondria. One is similar to that found in animals and is sensitive to (poisoned by) cyanide. The second pathway, which shares the initial steps of the first pathway, does not occur in animals and is cyanide resistant. This second, alternative pathway is less efficient than the first in energy production. Interest in the two pathways is heightened by the fact that plants can regulate the flow of electrons between the two pathways. Hence there are environmental and biological conditions that favor the use of one pathway or the other. The fact that the alternative pathway is less efficient energetically raises the question of why the second pathway exists and is preferred under certain conditions. The experiments outlined in this proposal to study the alternative oxidase will help to characterize the alternative oxidase and how it functions.

本研究旨在继续纯化和表征大多数植物、真菌和一些原生动物中与线粒体电子传递链相关的抗氰化物“替代”氧化酶。这种能量浪费的氧化酶在植物能量代谢中的作用尚不清楚，直到最近才取得进展，确定与氧化酶相关的蛋白质物种。该项目已成功地从开花臭鼬白菜的高抗氰化空间中部分纯化了替代氧化酶。该制剂将被进一步纯化，并与酶催化的氧还原反应相关的辅因子将被鉴定。更具体地说，发现与酶相关的可自氧化醌的性质和数量将被确定，与纯化酶结合的任何金属的性质也将被确定。还将进行研究，以确定立体因素、氧化还原电位和醌亲脂性对给定醌类作为替代氧化酶的电子供体的能力的相对贡献。这些研究将有助于更好地了解这种不寻常的氧化酶及其与线粒体电子传递链相互作用的性质。与人类等动物不同，植物的线粒体中有两条呼吸途径。一种与动物体内发现的相似，对氰化物敏感（中毒）。第二种途径与第一种途径的初始步骤相同，在动物中不发生，并且具有氰化物抗性。在能源生产中，第二种替代途径的效率低于第一种途径。植物可以调节这两种途径之间的电子流动，这一事实增强了人们对这两种途径的兴趣。因此，存在有利于使用其中一种途径的环境和生物条件。另一种途径在能量上效率较低，这一事实提出了为什么第二种途径存在并在某些条件下更受欢迎的问题。本文提出的研究替代氧化酶的实验将有助于表征替代氧化酶及其功能。