Kruger Nicholas J, Le Lay Pascaline, Ratcliffe R George
Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
Phytochemistry. 2007 Aug-Sep;68(16-18):2189-96. doi: 10.1016/j.phytochem.2007.04.004. Epub 2007 May 23.
Steady-state stable isotope labelling provides a method for generating flux maps of the compartmented network of central metabolism in heterotrophic plant tissues. Theoretical analysis of the contribution of the vacuole to the regeneration of glucose by endogenous processes shows that numerical fitting of isotopomeric data will only generate an accurate map of the fluxes involving intracellular glucose if information is available on the labelling of both the cytosolic and vacuolar glucose pools. In the absence of this information many of the calculated fluxes are at best unreliable or at worst indeterminate. This result suggests that the anomalously high rates of sucrose cycling and glucose resynthesis that have been reported in earlier steady-state analyses of tissues labelled with (13)C-glucose precursors may be an artefact of assuming that the labelling pattern of extracted glucose reflected the labelling of the cytosolic pool. The analysis emphasises that although subcellular information can sometimes be deduced from a steady-state analysis without recourse to subcellular fractionation, the success of this procedure depends critically on the structure of the metabolic network. It is concluded that methods need to be implemented that will allow measurement of the subcellular labelling pattern of glucose and other metabolites, as part of the routine analysis of the redistribution of label in steady-state stable isotope labelling experiments, if the true potential of network flux analysis for generating metabolic phenotypes is to be realized.
稳态稳定同位素标记提供了一种方法，用于生成异养植物组织中中心代谢的区室化网络的通量图。对液泡通过内源性过程对葡萄糖再生的贡献进行的理论分析表明，只有在获得胞质和液泡葡萄糖池的标记信息时，同位素异构体数据的数值拟合才能生成涉及细胞内葡萄糖的通量的准确图谱。在缺乏此信息的情况下，许多计算出的通量充其量是不可靠的，最坏的情况是不确定的。这一结果表明，在早期用(13)C-葡萄糖前体标记的组织的稳态分析中报道的异常高的蔗糖循环和葡萄糖再合成速率，可能是假设提取的葡萄糖的标记模式反映了胞质池的标记的人为产物。该分析强调，虽然有时可以在不进行亚细胞分级分离的情况下从稳态分析中推断出亚细胞信息，但该程序的成功关键取决于代谢网络的结构。得出的结论是，如果要实现网络通量分析生成代谢表型的真正潜力，就需要实施一些方法，以便在稳态稳定同位素标记实验中作为标记再分布常规分析的一部分，测量葡萄糖和其他代谢物的亚细胞标记模式。
