高等植物的交替氧化酶研究进展

The Study Progress of Alterative Oxidase in Higher Plant

交替氧化酶(Alternative Oxidase,AOX)广泛存在于高等植物、藻类和原生生物线粒体内膜。从主呼吸链的辅酶Q分岔,是氧化辅酶Q、还原氧分子生成水的另一终端氧化酶。氧化过程没有质子穿膜运动、热量以产热方式散发。产热植物中交替氧化产生的热量使花粉发出芳香味吸引虫传粉。推测植物AOX使植物在环境胁迫下维持呼吸,调节能量平衡,抵抗氧化胁迫,保持三羧酸循环的运行。AOX是首次发现的双铁羧酸蛋白质成员中的膜蛋白质,AOX与膜分离后容易失活,至今尚未有三级结构的报导,只有二级结构的2种假设模式,最新的模式AOX为膜界面蛋白质而不是跨膜蛋白。最近我们的研究表明有2个途径可获得适量有活性的AOX:建立优化的pFLAG-1-AOX大肠杆菌超量表达系统;从产热植物如斑叶阿若母(Arum maculatum)花序组织线粒体分离纯化有活性的AOX。

Alternative oxidase （AOX）, a terminal oxidase located in the inner mitochondrial membrane, has been identified universally in plant, algae, fungi, and protozoan. AOX branches from the cytochrome pathway at the level of the ubiquinone and catalyses the oxidation of ubiquinol and reduction of oxygen to water. There is non-protonmotive and energy is liberated as heat instead of producing ATP. In thermogenic plants, heat released by AOX attracts insects for pollination by heating aromatic compounds. The use of AOX in plant may （a） allow flexibility of respiration under changing environmental conditions （b） regulate energy homeostasis （c） help prevent oxidative stress （d） maintain TCA cycle turnover. AOX is a member of di-iron carboxylate proteins. Two structural models exist for AOX and the latest one is a monotopic protein instead of span membrane. Relatively little is known about its 3-dimensional structure. Main reason is that the sufficient quantities of AOX suitable for crystallogram structural studies is unavailable because of its unstableness. Recently we tried to obtain sufficient quantities alternative oxidaae protein （AOX） for further construction studies. The aim is achieved by over-expressing in E. coli and improving purification of native AOX from Arran mitochondrial.