Light-Dependent Uptake of Pyruvate by Mesophyll Chloroplasts of a C4 Plant, Panicum miliaceum L.
Light-Dependent Uptake of Pyruvate by Mesophyll Chloroplasts of a C4 Plant, Panicum miliaceum L.
复制标题
C4 植物黍叶肉叶绿体对丙酮酸的光依赖性吸收。
DOI：
10.1093/oxfordjournals.pcp.a077290
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
R. Kanai
中科院分区：
文献类型：
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作者：
J. Ohnishi;R. Kanai
据报道，C4 植物 Panicum miliaceum 的叶肉叶绿体中丙酮酸的光依赖性主动吸收[Ohnishi 和 Kanai (1987)Plant Cell Physiol. 28：1]。本研究试图阐明这种主动摄取的能量来源。叶肉叶绿体的预光照使它们在光照和黑暗中的丙酮酸吸收量增加了十倍以上。这表明光本身对于增强来说并不是必需的。叶肉叶绿体的丙酮酸吸收能力（初始吸收率）在光照下增加，并在几分钟后达到稳态水平；在较高的光强度下，这种上升速度更快。当叶绿体回到黑暗中时，吸收能力衰减，半衰期约为1分钟；这与预照明的光强度无关。叶绿体的光照还将基质 pH 从约 7 增加到 8，基质 ATP 水平从约 5 增加到 15-25 nmol。 (毫克叶绿素)−1。前者在从暗到亮和从亮到暗的转变过程中的变化发生在2至5分钟内，而后者的变化在1分钟内发生得更快。丙酮酸摄取能力和基质 pH 的稳态水平在光强度为 3 μE.m−2.s−1 时达到饱和，而 ATP 水平随着光强度的进一步增加而增加。前两个参数对羰基氰-间氯苯腙的抑制也表现出相似的敏感性，而需要更高浓度的抑制剂来降低 ATP 水平。 4mm亚硝酸盐抑制光依赖性丙酮酸摄取和基质碱化，但对基质ATP水平几乎没有影响，而2mm砷酸盐降低基质ATP，但对丙酮酸摄取和基质pH没有显着影响。丙酮酸吸收和基质 pH 值的良好相关性表明，叶肉叶绿体的活性丙酮酸吸收主要是由包膜上的 pH 梯度驱动的。
Light-dependent active uptake of pyruvate was reported in mesophyll chloroplasts of a C4plant,Panicum miliaceum[Ohnishi and Kanai (1987)Plant Cell Physiol. 28: 1]. The present study tried to clarify the energy source of this active uptake. Preillumination of the mesophyll chloroplasts increased over tenfold their pyruvate uptake in the light and dark. This indicates that light itself is not essential for the enhancement. The pyruvate uptake capacity (the initial uptake rate) of the mesophyll chloroplasts increased on illumination and reached a steady-state level after a few minutes; this rise was faster under higher light intensities. When the chloroplasts were returned to darkness, the uptake capacity decayed with a half-life of about 1 min; this was independent of the light intensity of preillumination. Illumination of the chloroplasts also increased the stromal pH from about 7 to 8 and the stromal ATP level from about 5 to 15–25 nmol. (mg chl)−1. The change of the former during dark-to-light and light-to-dark transitions occurred within 2 to 5 min, while the change of the latter took place much faster within 1 min. The steady-state levels of the pyruvate uptake capacity and stromal pH were saturated at a light intensity of 3 μE.m−2.s−1, while the ATP level increased with a further increase in the light intensity. The former two parameters also showed similar sensitivity to the inhibition by carbonylcyanide-m-chlorophenylhydrazone, while a higher concentration of the inhibitor was needed to reduce the ATP level. Nitrite at 4 mminhibited the light-dependent pyruvate uptake and stromal alkalization but had little effect on the stromal ATP level, while 2 mmarsenate decreased the stromal ATP without significant effects on pyruvate uptake and stromal pH. The good correlation of pyruvate uptake and stromal pH suggests that the active pyruvate uptake by the mesophyll chloroplasts is primarily driven by the pH gradient across the envelope.