Hoefnagel MHN., Wiskich J. T.
Department of Botany, University of Adelaide, Adelaide, SA 5005, Australia.
Plant Physiol. 1996 Apr;110(4):1329-1335. doi: 10.1104/pp.110.4.1329.
In Arum and soybean (Glycine max L.) mitochondria, the dependence of the alternative oxidase activity on the redox level of ubiquinone, with NADH and succinate as substrates, was studied, using a voltametric procedure to measure the ubiquinone redox poise in the mitochondrial membrane. The results showed that when the enzyme was activated by pyruvate the relationship between the alternative oxidase rate and the redox state of the ubiquinone pool was the same for both NADH and succinate oxidations. In the absence of pyruvate the alternative oxidase had an apparent lower affinity for ubiquinol. This was more marked with NADH than with succinate and was possibly due to pyruvate production during succinate oxidation or to an activation of the alternative oxidase by succinate itself. In Arum spadix (unlike soybean cotyledon) mitochondria, succinate oxidation via the alternative oxidase maintained the ubiquinone pool in a partially reduced state (60%), whereas NADH oxidation kept it almost completely reduced. Previous data comparing mitochondria from thermogenic and nonthermogenic tissues have not examined the full range of ubiquinone redox levels in both tissues, leading to the suggestion that the activity of alternative oxidase for Arum was different from nonthermogenic tissues. When the complete range of redox states of ubiquinone is used and the oxidase is fully activated, the alternative oxidase from thermogenic tissue (Arum) behaves similarly to that of nonthermogenic tissue (soybean).
在魔芋和大豆（Glycine max L.）线粒体中，以NADH和琥珀酸为底物，利用伏安法测量线粒体膜中泛醌的氧化还原状态，研究了交替氧化酶活性对泛醌氧化还原水平的依赖性。结果表明，当该酶被丙酮酸激活时，对于NADH和琥珀酸氧化，交替氧化酶速率与泛醌池氧化还原状态之间的关系是相同的。在没有丙酮酸的情况下，交替氧化酶对泛醇的亲和力明显较低。这在以NADH为底物时比以琥珀酸为底物时更明显，可能是由于琥珀酸氧化过程中产生了丙酮酸，或者是琥珀酸本身激活了交替氧化酶。在魔芋佛焰苞（与大豆子叶不同）线粒体中，通过交替氧化酶进行的琥珀酸氧化使泛醌池保持在部分还原状态（60%），而NADH氧化则使其几乎完全还原。先前比较产热组织和非产热组织线粒体的研究并未考察这两种组织中泛醌氧化还原水平的完整范围，从而有人提出魔芋交替氧化酶的活性与非产热组织不同。当使用泛醌完整的氧化还原状态范围且氧化酶完全激活时，产热组织（魔芋）中的交替氧化酶与非产热组织（大豆）中的表现相似。
