Title: 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.
Citation: PLANT CELL AND ENVIRONMENT vol. 34 no. 7 p. 1104-1112
Publication Year: 2011
JRC N°: JRC57790
ISSN: 0140-7791
URI: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2011.02308.x/abstract
DOI: 10.1111/j.1365-3040.2011.02308.x
Type: Articles in periodicals and books
Abstract: 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 (d13Ci, ‰) 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 delta 18O 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 delta 13Ci -values in ethanol reflect that in source glucose, our data point out the crucial impact on the ratio of metabolic pathways sustaining glucose synthesis.
JRC Directorate:Institute for Health and Consumer Protection Historical Collection

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