A comparison of the relative rates of transport of ascorbate and glucose across the thylakoid, chloroplast and plasmalemma membranes of pea leaf mesophyll cells
A comparison of the relative rates of transport of ascorbate and glucose across the thylakoid, chloroplast and plasmalemma membranes of pea leaf mesophyll cells
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DOI：
10.1016/s0176-1617(96)80271-9
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发表时间：
1996-05-01
影响因子：
4.3
通讯作者：
Lelandais, M
中科院分区：
文献类型：
--
作者：
Foyer, CH;Lelandais, M
从10-12天龄豌豆幼苗叶片中制备叶肉原生质体、叶绿体和类囊体。每毫克叶绿素分别含有1618 +/- 351、197 +/- 30和25 +/- 7 nmol抗坏血酸盐，相当于完整原生质体、完整叶绿体和类囊体膜中抗坏血酸盐的平均浓度分别为8.4、9.8和3.8 mM。运输[C-14]-抗坏血酸和[C-14]-葡萄糖跨质膜，叶绿体被膜和类囊体膜测定在这些馏分。[C-14]-抗坏血酸和[C-14]-葡萄糖摄取的饱和动力学表明质膜和叶绿体被膜含有抗坏血酸和葡萄糖的载体。相反，类囊体膜似乎没有抗坏血酸的运输系统，渗透性仅由扩散引起。脱氢抗坏血酸抑制抗坏血酸的运输，但没有葡萄糖运输通过叶绿体被膜。抗坏血酸刺激[C-14]-葡萄糖跨质膜和叶绿体被膜的运输。同样，葡萄糖有积极的影响：[C-14]抗坏血酸跨这些膜的运输。这些观察结果表明，抗坏血酸和葡萄糖到原生质体和叶绿体的独立载体的存在。不像动物膜中的己糖转运蛋白已被发现运输脱氢抗坏血酸的植物同行似乎不这样做，无论是在叶绿体被膜或质膜。因此，这些膜上的抗坏血酸转运蛋白是不参与一般己糖转运的离散实体。然而，所观察到的协同效应，无论是葡萄糖或抗坏血酸对其他代谢物的运输建议协调的两个过程。
Mesophyll protoplasts, chloroplasts and thylakoids were prepared from the leaves of 10-12 day old pea seedlings. They contained 1618 +/- 351, 197 +/- 30 and 25 +/- 7 nmol ascorbate per milligram of chlorophyll respectively equivalent to average concentrations of 8.4, 9.8 and 3.8 mM ascorbate in the intact protoplasts, intact chloroplasts and thylakoid membranes respectively. Transport of [C-14]-ascorbate and [C-14]-glucose across the plasmalemma, chloroplast envelope and thylakoid membranes was measured in these fractions. Saturation kinetics for [C-14]-ascorbate and [C-14]-glucose uptake suggest that the plasmalemma and chloroplast envelope membranes contain carriers for both ascorbate and glucose. In contrast, the thylakoid membranes appear to have no transport system for ascorbate, permeability resulting from diffusion alone. Dehydroascorbate inhibited ascorbate transport but not glucose transport across the chloroplast envelope membrane. Ascorbate stimulated [C-14]-glucose transport across the plasmalemma and chloroplast envelope membranes. Similarly, glucose had a positive effect: on [C-14] ascorbate transport across these membranes. These observations suggest the presence of independent carriers for ascorbate and glucose into both protoplasts and chloroplasts. Unlike animal membranes where the hexose transporters have been found to transport dehydroascorbate the plant counterparts does not appear to do so, either in the chloroplast envelope or the plasmalemma membranes. The ascorbate transporters on these membranes are hence discrete entities not involved with general hexose transport. However, the observed synergistic effects of either glucose or ascorbate on the transport of the other metabolite suggest co-ordination of the two processes.