Development of Chemical Analysis for Metabolic Intermediates

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Most of the metabolites in living cells or tissues are polar and ionic substances that are not suitable for chemical analysis by using conventional methods such as GC-and LC-MS. We have successfully developed capillary electrophoresis coupled with mass spectrometry (CE-MS) as a method of metabolomics. We applied the method to analyze the metabolic intermediates of the central energy metabolism of the Bacillus subtilis cells and compared the metabolite profiles that schematically show the intercellular amount of the metabolites on the central metabolic pathways of the cells cultured under various environmental and genetic perturbations. The metabolite profiles were globally same when the rates of the cell division were the same under the different perturbations. This suggests that B. subtilis has a metabolite profile that is optimized for its cell division and that it maintain the profile against the environmental and genetic perturbations. At the same times when we analyzed the metabolites, we measured the gene expressions by using the DNA microarray of B. subtilis. Gene expression data were overlaid on the metabolite profiles. When perturbations were not so different from the control experiment, amount of the expressions of several enzyme genes were regulated. On the others where perturbations were quite different, B. subtilis changed not only gene expressions but also metabolic pathways; it used a quite different metabolic pathways from those of the control experiment. These results suggests that the metabolite profile is quantitatively and qualitatively regulated; this must be a way of "homeostasis". It is most likely that each living species has its own metabolite profile for cell division.