REDOX TRANSFER ACROSS THE INNER CHLOROPLAST ENVELOPE MEMBRANE
REDOX TRANSFER ACROSS THE INNER CHLOROPLAST ENVELOPE MEMBRANE
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DOI：
10.1104/pp.95.4.1131
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发表时间：
1991-04-01
期刊：
影响因子：
7.4
通讯作者：
HELDT, HW
中科院分区：
文献类型：
--
作者：
HEINEKE, D;RIENS, B;HELDT, HW
菠菜(Spinacia holacea L.)利用非水相分离技术，在光照和黑暗条件下分别测定了在CO2环境中生长的亚细胞内腺苷酸、吡啶核苷酸、3-磷酸甘油酸、二羟丙酮磷酸、苹果酸、谷氨酸、2-羟基戊二酸和天冬氨酸的含量。根据测定的光照叶片叶绿体部分中NADP和NADPH的浓度，计算出基质NADPH/NADP的比值为0.5。对于胞浆，根据NAD、苹果酸、谷氨酸、天冬氨酸和2-羟基戊二酸浓度的测定，假设胞液中谷氨酸草酰乙酸转氨酶和苹果酸脱氢酶催化的反应离平衡不远，则NADH/NAD的比值为10(-3)。在将氧化还原等价物从叶绿体NADPH转移到细胞质NAD的过程中，有两个代谢物穿梭穿过内被膜：磷酸丙糖-3-磷酸甘油酯穿梭和苹果酸-草酰乙酸酯穿梭。虽然这两个航天飞机都有能力使基质和胞质间的氧化还原状态变平，但显然没有发生这种情况。为了深入了解调控过程，我们计算了酶反应和涉及的转位步骤的自由能。结果表明，磷酸丙糖-3-磷酸甘油酸酯穿梭主要受3-磷酸甘油酸还原的氯塑性反应和磷酸丙糖氧化的胞浆反应控制。苹果酸-草酰乙酸酯穿梭受到叶绿体NADP-苹果酸脱氢酶和跨膜转运步骤的调控。
In leaves of spinach plants (Spinacia oleracea L.) grown in ambient CO2 the subcellular contents of adenylates, pyridine nucleotides, 3-phosphoglycerate, dihydroxyacetone phosphate, malate, glutamate, 2-oxoglutarate, and aspartate were assayed in the light and in the dark by nonaqueous fractionation technique. From the concentrations of NADP and NADPH determined in the chloroplast fraction of illuminated leaves the stromal NADPH to NADP ratio is calculated to be 0.5. For the cytosol a NADH to NAD ratio of 10(-3) is calculated from the assay of the concentrations of NAD, malate, glutamate, aspartate, and 2-oxoglutarate on the assumption that the reactions catalyzed by the cytosolic glutamate oxaloacetate transaminase and malate dehydrogenase are not far away from equilibrium. For the transfer of redox equivalents from the chloroplastic NADPH to the cytosolic NAD two metabolite shuttles are operating across the inner envelope membrane: the triosephosphate-3-phosphoglycerate shuttle and the malate-oxaloacetate shuttle. Although both shuttles would have the capacity to level the redox state of the stromal and cytosolic compartment, this apparently does not occur. To gain an insight into the regulatory processes we calculated the free energy of the enzymic reactions and of the translocation steps involved. From the results it is concluded that the triosephosphate-3-phosphoglycerate shuttle is mainly controlled by the chloroplastic reaction of 3-phosphoglycerate reduction and of the cytosolic reaction of triosephosphate oxidation. The malate-oxaloacetate shuttle is found to be regulated by the chloroplastic NADP-malate dehydrogenase and also by the translocating step across the envelope membrane.