Metabolic flux analysis in complex isotopolog space. Recycling of glucose in tobacco plants

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• 作者：Ettenhuber ; Christian ; Radykewicz ; Tanja ; Kofer ; Waltraud ; Koop ; Hans-Ulrich ; Bacher ; Adelbert ; et. al.
• 关键词：Nicotiana tabacum ; Metabolism ; Carbon flux ; NMR ; Isotopolog ; In silico modelling
• 刊名：Phytochemistry
• 出版年：2005
• 出版时间：February, 2005
• 年：2005
• 卷：66
• 期：3
• 页码：323-335
• 全文大小：446 K

文摘

Tobacco plants grown in vitro were supplied with a mixture of [U-¹³C₆]glucose and unlabelled sucrose via the root system. After 20 days, leaves were harvested and extracted with water. Glucose was isolated from the extract and was analysed by ¹³C NMR spectroscopy. All ¹³C signals appeared as complex multiplets due to ¹³Caaa¹³C coupling. The abundance of 21 isotopologous glucose species was determined from the ¹³C NMR signal integrals by numerical deconvolution using a genetic algorithm. The relative fractions of specific isotopologs in the overall excess of ¹³C-labelled specimens establish flux contributions via glycolysis/glucogenesis, pentose phosphate pathway, citric acid cycle and Calvin cycle including ¹³CO₂ refixation. The fluxes were modelled and reconstructed in silico by a novel rule-based approach yielding the contributions of circular pathways and the degree of multiple cycling events. The data indicate that the vast majority of the proffered [U-¹³C₆]glucose molecules had been modified by catabolism and subsequent glucogenesis from catabolic fragments, predominantly via passage through the citric acid cycle and the pentose phosphate pathway.