Intramolecular deuterium distributions reveal disequilibrium of chloroplast phosphoglucose isomerase
Intramolecular deuterium distributions reveal disequilibrium of chloroplast phosphoglucose isomerase
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DOI：
10.1046/j.1365-3040.1999.00440.x
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发表时间：
1999-05-01
影响因子：
7.3
通讯作者：
Sharkey, TD
中科院分区：
文献类型：
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作者：
Schleucher, J;Vanderveer, P;Sharkey, TD
使用氘核磁共振测量葡萄糖的碳结合氢的分子内氘分布。与从叶蔗糖或豆类胚乳淀粉中分离的葡萄糖相比，从菜豆（Phaseolus vulgaris cv，Linden）或菠菜（Spinacia oleracea cv，Giant nobel）的叶淀粉中分离的葡萄糖在C（2）位置上氘被耗尽。在豆类中，C（2）的消耗与生长过程中的光强度（150或700 mu mol光子）无关。 s(-1) m(-2))。豆类叶绿体中葡萄糖-6-磷酸与果糖-6-磷酸（[G6P]/[F6P]）的比率（[G6P]/[F6P]）在高光下为0.9，表明磷酸葡萄糖异构酶反应未达到平衡（[G6P]/[F6P]）接近3），这意味着磷酸葡萄糖异构酶的动力学同位素效应耗尽了豆类C（2）位的氘。 G6P，由于消耗相同，因此无论光强度如何，叶绿体（[G6P]/[F6P]）比率都处于不平衡状态。如果 ([G6P]/[F6P]) 比例处于平衡状态，则大量 G6P 叶绿体池将无法用于核酮糖-1,5-二磷酸的再生。我们认为调节叶绿体磷酸葡萄糖异构酶活性可以避免这种情况。 C(2) 的氘消耗解释了已知的叶淀粉总体氘丰度较低的原因。这个例子表明，分子内氘分布的测量对于了解植物材料的总体氘丰度至关重要。
Intramolecular deuterium distributions of the carbon-bound hydrogens of glucose were measured using deuterium nuclear magnetic resonance. Glucose isolated from leaf starch of common bean (Phaseolus vulgaris cv, Linden) or spinach (Spinacia oleracea cv, Giant nobel) was depleted in deuterium in the C(2) position, compared with glucose isolated from leaf sucrose or bean endosperm starch, In beans, the depletion of C(2) was independent of the light intensity during growth (150 or 700 mu mol photons s(-1) m(-2)). The ratio of glucose-6-phosphate to fructose-6-phosphate ([G6P]/[F6P]) in bean chloroplasts was 0.9 in high light, indicating that the phosphoglucose isomerase reaction was not in equilibrium ([G6P]/[F6P]) approximate to 3), This implies that the kinetic isotope effect of phosphoglucose isomerase depleted deuterium in the C(2) position of G6P, Because the depletion was the same, the chloroplastic ([G6P]/[F6P]) ratio was in disequilibrium irrespective of the light intensity. If the ([G6P]/[F6P]) ratio was in equilibrium, a large chloroplastic pool of G6P would be unavailable for regeneration of ribulose-1,5-bisphospate. We argue that chloroplast phosphoglucose isomerase activity is regulated to avoid this. The deuterium depletion of C(2) explains the known low overall deuterium abundance of leaf starch. This example shows that measurements of intramolecular deuterium distributions can be essential to understand overall deuterium abundances of plant material.