Malate Oxidation in Plant Mitochondria via Malic Enzyme and the Cyanide-insensitive Electron Transport Pathway.
Malate Oxidation in Plant Mitochondria via Malic Enzyme and the Cyanide-insensitive Electron Transport Pathway.
复制标题
通过苹果酸酶和氰化物不敏感电子传输途径对植物线粒体中的苹果酸氧化。
作者：
P. Rustin;F. Moreau;C. Lance
植物线粒体中的苹果酸氧化通过两种酶的活性进行：苹果酸脱氢酶和NAD（+）依赖的苹果酸酶。在花椰菜中，线粒体苹果酸氧化通过苹果酸脱氢酶是鱼藤酮和氰化物敏感。外源NAD（+）的加入刺激苹果酸通过苹果酸酶的氧化，并产生一个电子通量，这是鱼藤酮和氰化物不敏感。外源NAD（+）对来自白色马铃薯块茎的高度氰化物敏感的线粒体或来自菠菜叶的线粒体也观察到相同的作用。两种酶均位于基质中，但一些实验数据也表明部分苹果酸脱氢酶活性也存在于基质隔室之外（吸附的胞质苹果酸脱氢酶？）。结论是苹果酸酶和NAD（+）/NADH的特定池通过位于内膜内表面的特定鱼藤酮不敏感的NADH脱氢酶连接到氰化物不敏感的替代途径。类似地，苹果酸脱氢酶和另一个特定的NAD（+）/NADH库通过位于内膜内表面的鱼藤酮敏感性NADH脱氢酶连接到氰化物敏感性途径（和抗霉素敏感性途径）。假设不同的泛醌库作为不同的脱氢酶、氰化物敏感的细胞色素途径和氰化物不敏感的交替途径之间的分支点，可以给出植物线粒体中苹果酸和NADH氧化的电子传递的一般方案。
MALATE OXIDATION IN PLANT MITOCHONDRIA PROCEEDS THROUGH THE ACTIVITIES OF TWO ENZYMES: a malate dehydrogenase and a NAD(+)-dependent malic enzyme. In cauliflower, mitochondria malate oxidation via malate dehydrogenase is rotenone- and cyanide-sensitive. Addition of exogenous NAD(+) stimulates the oxidation of malate via malic enzyme and generates an electron flux that is both rotenone- and cyanide-insensitive. The same effects of exogenous NAD(+) are also observed with highly cyanide-sensitive mitochondria from white potato tubers or with mitochondria from spinach leaves. Both enzymes are located in the matrix, but some experimental data also suggest that part of malate dehydrogenase activity is also present outside the matrix compartment (adsorbed cytosolic malate dehydrogenase?). It is concluded that malic enzyme and a specific pool of NAD(+)/NADH are connected to the cyanide-insensitive alternative pathway by a specific rotenone-insensitive NADH dehydrogenase located on the inner face of the inner membrane. Similarly, malate dehydrogenase and another specific pool of NAD(+)/NADH are connected to the cyanide- (and antimycin-) sensitive pathway by a rotenone-sensitive NADH dehydrogenase located on the inner face of the inner membrane. A general scheme of electron transport in plant mitochondria for the oxidation of malate and NADH can be given, assuming that different pools of ubiquinone act as a branch point between various dehydrogenases, the cyanide-sensitive cytochrome pathway and the cyanide-insensitive alternative pathway.