Department of Cellular and Molecular Biology, Division of Biological Sciences, University of Michigan, Ann Arbor, Michigan 48104.
Plant Physiol. 1976 Sep;58(3):433-7. doi: 10.1104/pp.58.3.433.
In order to investigate the relationship between malate oxidation and subsequent cycle reactions, the effects of oxaloacetate, pyruvate, and thiamine pyrophosphate on malate oxidation in mung bean (Phaseolus aureus var. Jumbo) hypocotyl mitochondria were quantitatively examined. Malate oxidation was optimally stimulated by addition of pyruvate and thiamine pyrophosphate, whose addition lowered the apparent Km for malate from 5 mm to 0.1 mm. Intermediate analysis showed that the stimulatory effect was correlated with removal of oxaloacetate to citrate. Oxaloacetate added alone was shown not to be metabolized until addition of pyruvate and thiamine pyrophosphate; then oxaloacetate was converted in part to pyruvate and also to citrate. These results establish that malate oxidation in mung bean mitochondria is subject to control by oxaloacetate levels, which are primarily determined by the resultant of the activities of malate dehydrogenase, citrate synthase, and pyruvate dehydrogenase.
为了研究苹果酸氧化与随后的循环反应之间的关系，定量研究了草酰乙酸、丙酮酸和焦磷酸硫胺素对绿豆（Phaseolus aureus var. Jumbo）下胚轴线粒体中苹果酸氧化的影响。丙酮酸和焦磷酸硫胺素的添加最能刺激苹果酸氧化，其添加将苹果酸的表观 Km 值从 5mm 降低到 0.1mm。中间分析表明，这种刺激作用与草酰乙酸向柠檬酸的去除有关。单独添加草酰乙酸，直到添加丙酮酸和焦磷酸硫胺素后才被代谢；然后草酰乙酸部分转化为丙酮酸，也转化为柠檬酸。这些结果表明，绿豆线粒体中的苹果酸氧化受到草酰乙酸水平的控制，而草酰乙酸水平主要由苹果酸脱氢酶、柠檬酸合酶和丙酮酸脱氢酶的活性决定。
