The intramolecular ¹³C-distribution in ethanol reveals the influence of the CO₂ -fixation pathway and environmental conditions on the site-specific ¹³C variation in glucose.
The intramolecular ¹³C-distribution in ethanol reveals the influence of the CO₂ -fixation pathway and environmental conditions on the site-specific ¹³C variation in glucose.
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DOI：
10.1111/j.1365-3040.2011.02308.x
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发表时间：
2011-07
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影响因子：
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通讯作者：
A. Gilbert;Virginie Silvestre;Nicolas Segebarth;G. Tcherkez;C. Guillou;R. Robins;S. Akoka;G. Remaud
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文献类型：
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作者：
A. Gilbert;Virginie Silvestre;Nicolas Segebarth;G. Tcherkez;C. Guillou;R. Robins;S. Akoka;G. Remaud
由于缺乏代谢产物中C的分子内分布及其随环境条件变化的数据，理解植物光合作用和光合后代谢过程中C与C同位素分馏的原因的努力受到挫折。我们利用同位素碳-13核磁共振（C NMR）光谱法测量了来自不同来源的乙醇样品中的位置同位素组成（δ C（i），‰）：欧洲葡萄酒，白酒和糖从C12，C13和景天科酸代谢（CAM）植物。在C β-乙醇样品中，亚甲基相对于甲基总是富集C（约2‰）。在葡萄酒中，这种模式与空气温度和葡萄酒水的δ（18）O相关，表明水蒸气不足可能是一个关键的决定因素。此外，在C β-乙醇中，观察到相反的关系（亚甲基-C相对C耗尽），支持光呼吸是导致C β-乙醇中C分布的关键代谢过程的概念。相比之下，在CAM-乙醇中，同位素模式类似于但比C-乙醇更强，亚甲基-C的相对碳富集高达13‰。本文简要讨论了这种C型的可能原因。由于乙醇中的分子内δ C（i）值反映了源葡萄糖中的δ C（i）值，因此我们的数据指出了对维持葡萄糖合成的代谢途径比率的关键影响。
Efforts to understand the cause of ¹²C versus ¹³C isotope fractionation in plants during photosynthesis and post-photosynthetic metabolism are frustrated by the lack of data on the intramolecular ¹³C-distribution in metabolites and its variation with environmental conditions. We have exploited isotopic carbon-13 nuclear magnetic resonance (¹³C NMR) spectrometry to measure the positional isotope composition (δ¹³C(i) , ‰) in ethanol samples from different origins: European wines, liquors and sugars from C₃, C₄ and crassulacean acid metabolism (CAM) plants. In C₃-ethanol samples, the methylene group was always ¹³C-enriched (∼2‰) relative to the methyl group. In wines, this pattern was correlated with both air temperature and δ(18)O of wine water, indicating that water vapour deficit may be a critical defining factor. Furthermore, in C₄-ethanol, the reverse relationship was observed (methylene-C relatively ¹³C-depleted), supporting the concept that photorespiration is the key metabolic process leading to the ¹³C distribution in C₃-ethanol. By contrast, in CAM-ethanol, the isotopic pattern was similar to but stronger than C₃-ethanol, with a relative ¹³C-enrichment in the methylene-C of up to 13‰. Plausible causes of this ¹³C-pattern are briefly discussed. As the intramolecular δ¹³C(i) -values in ethanol reflect that in source glucose, our data point out the crucial impact on the ratio of metabolic pathways sustaining glucose synthesis.