Characterization of the Cyanide-resistant Oxidase in Plant Mitochondria

本提案中概述的研究旨在继续 抗氰， 与电子转移链相关的“交替”氧化酶 大多数植物、许多真菌和一些原生动物的线粒体。 的 这种能量浪费氧化酶在植物能量中的作用 代谢是未知的，直到最近才取得进展 鉴定与氧化酶相关的蛋白质种类。 的PI 成功地进行了部分纯化， 来自高抗氰化物的spadices的交替氧化酶 开花臭鼬甘蓝 该制剂将进一步纯化 和与氧还原反应相关的辅因子 由酶催化的将被识别。 更具体而言是 发现可自氧化的醌的性质和量 与酶相关的性质将被确定， 与纯化酶结合的金属元素 研究还将 进行，以确定空间的相对贡献 氧化还原电位和醌亲脂性的能力 给定的醌类物质作为电子供体， 交替氧化酶 这些研究将导致更好的下 了解这种不寻常的氧化酶及其性质 与线粒体电子传递链的相互作用。 与人类等动物不同，植物有两个呼吸系统。 线粒体中的通路。 其中一个类似于 对氰化物敏感（中毒）。 第二 途径，它共享第一途径的初始步骤， 不会发生在动物身上，并且是抗氰化物的。 这一秒， 替代途径在能量方面不如第一种途径有效 生产 人们对这两种途径的兴趣因以下事实而增加： 植物可以调节两者之间的电子流动 途径。 因此有环境和生物条件 倾向于使用一种途径或另一种途径。 的事实 替代途径的效率较低， 为什么第二种途径存在，并且在 一定条件 本提案中概述的实验旨在 研究替代氧化酶将有助于表征 替代氧化酶及其功能。

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.