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己糖激酶在豌豆叶片中的线粒体定位。

The mitochondrial localization of hexokinase in pea leaves.

机构信息

Department of Botany, University of Adelaide, 5001, Adelaide, S.A., Australia.

出版信息

Planta. 1983 Jun;158(2):152-6. doi: 10.1007/BF00397708.

Abstract

Up to 80% of total cellular hexokinase (EC 2.1.7.4) activity in pea (Pisum sativum L.) leaves was found to be associated with particulate fractions. Fractionation on sucrose density gradients showed this particulate activity to be associated exclusively with mitochondria. In the presence of glucose and ATP, the bound mitochondrial hexokinase could support rates of O2 uptake of up to 30% of normal ADP-stimulated rates. This stimulation of O2 uptake by hexokinase was completely sensitive to oligomycin, indicating that it resulted from an increase in the supply of ADP for mitochondrial oxidative phosphorylation. Spectrophotometric measurements of the mitochondrial hexokinase activity showed that ADP could support rapid rates of activity provided oxidizable substrates were also present to support the conversion of ADP to ATP in oxidative phosphorylation. Carboxyatractyloside, an inhibitor of adenine-nucleotide uptake by mitochondria, inhibited this ADP-supported activity, but had no effect on hexokinase activity in the presence of added ATP, demonstrating that the hexokinase enzyme was located external to the inner mitochondrial membrane. Oligomycin also inhibited ADP-supported activity but had no effect on ATP-supported hexokinase activity. Glucose (Km 53 μM) was the preferred substrate of pea-leaf mitochondrial hexokinase compared with fructose (Km 5.1 mM). Hexokinase was not solubilised in the presence of glucose-6-phosphate.

摘要

豌豆叶片中高达 80%的细胞总己糖激酶(EC 2.1.7.4)活性与颗粒部分相关。蔗糖密度梯度分级显示,这种颗粒活性仅与线粒体有关。在葡萄糖和 ATP 的存在下,结合的线粒体己糖激酶可以支持高达 30%的正常 ADP 刺激的 O2 摄取速率。己糖激酶对 O2 摄取的这种刺激完全对寡霉素敏感,表明它是由于 ADP 供应增加,用于线粒体氧化磷酸化。对线粒体己糖激酶活性的分光光度测量表明,ADP 可以支持快速的活性速率,只要存在可氧化的底物来支持 ADP 在氧化磷酸化中转化为 ATP。羧基甜菜碱,一种抑制线粒体摄取腺嘌呤核苷酸的抑制剂,抑制了这种 ADP 支持的活性,但对添加的 ATP 存在下的己糖激酶活性没有影响,表明己糖激酶酶位于线粒体内膜之外。寡霉素也抑制 ADP 支持的活性,但对 ATP 支持的己糖激酶活性没有影响。与果糖(Km 5.1 mM)相比,葡萄糖(Km 53 μM)是豌豆叶线粒体己糖激酶的首选底物。己糖激酶在葡萄糖-6-磷酸存在下不能溶解。

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