Department of Horticulture, University of Illinois, Urbana, Illinois 61801.
Plant Physiol. 1968 Jul;43(7):1108-14. doi: 10.1104/pp.43.7.1108.
Experimental conditions which optimize both substrate- and ATP-dependent Ca(2+) transport in corn (Zea mays) mitochondria have been determined. It has been found that a substrate (pyruvate + succinate) dependent, Pi independent, binding of Ca(2+) occurs. This reaction is very rapid and complete in less than 30 seconds. For massive accumulation of calcium, Pi is essential. Phosphate is accumulated along with the calcium and the ratio of Ca:Pi accumulated is about 1.6:1 indicating the precipitation of hydroxyapatite inside the mitochondria.The activation energies and Michaelis constants for both the substrate- and ATP-driven reactions have been determined. It has also been shown that the substrate-driven system is more efficient in Ca(2+) accumulation than the ATP-driven system. This is partially due to the fact that Mg(2+) is essential for the ATP-driven system but not for the substrate-driven system and that Mg(2+) acts as a strong competitor of Ca(2+) transport. The effect of other inorganic ions on Ca(2+) transport energized by both substrate and ATP were examined.The results lend support to the hypothesis that high energy intermediates of oxidative phosphorylation participate directly in Ca(2+) binding and transport in plant mitochondria.
已经确定了优化玉米（Zea mays）线粒体中底物和 ATP 依赖性 Ca(2+)转运的实验条件。已经发现，存在一种依赖于底物（丙酮酸+琥珀酸）、Pi 非依赖性的 Ca(2+)结合反应。该反应非常迅速，在不到 30 秒内即可完成。对于大量钙的积累，Pi 是必不可少的。磷与钙一起被积累，并且积累的 Ca:Pi 比值约为 1.6:1，表明羟磷灰石在内质体中沉淀。已经确定了底物和 ATP 驱动反应的活化能和米氏常数。还表明，与 ATP 驱动系统相比，底物驱动系统在 Ca(2+)积累方面更有效。这部分是由于以下事实：Mg(2+)对于 ATP 驱动系统是必需的，但对于底物驱动系统不是必需的，并且 Mg(2+)作为 Ca(2+)转运的强竞争物起作用。还研究了其他无机离子对由底物和 ATP 驱动的 Ca(2+)转运的影响。这些结果支持这样的假设，即氧化磷酸化的高能中间产物直接参与植物线粒体中的 Ca(2+)结合和转运。
