13C tracer experiments and metabolite balancing for metabolic flux analysis: Comparing two approaches

Isotopolog perturbation techniques for metabolic networks: Metabolic recycling of nutritional glucose inDrosophila melanogaster

“…All 13 C signals of the isolated glucose were multiplets arising by 13 C 13 C coupling. Based on a comprehensive analysis of the coupling constants and heavy isotope shifts in glucose, the integrals of individual 13 C signal patterns afforded the concentrations of certain groups of 13 C isotopologs. These data were deconvoluted by a genetic algorithm affording the abundances of all single-labeled and of 15 multiply labeled isotopologs.…”

“…One to two days after hatching, flies were extracted with water. Glucose was isolated chromatographically from the extract and was analyzed by 13 C NMR spectroscopy. All 13 C signals of the isolated glucose were multiplets arising by 13 C 13 C coupling.…”

“…Glucose was isolated chromatographically from the extract and was analyzed by 13 C NMR spectroscopy. All 13 C signals of the isolated glucose were multiplets arising by 13 C 13 C coupling. Based on a comprehensive analysis of the coupling constants and heavy isotope shifts in glucose, the integrals of individual 13 C signal patterns afforded the concentrations of certain groups of 13 C isotopologs.…”

“…Among the latter group, seven isotopologs were found at concentrations >0.1 mol % with [1,2-13 C2]glucose as the most prominent species. The multiply 13 Clabeled glucose isotopologs are caused by metabolic remodeling of the proffered glucose via a complex network of catabolic and anabolic processes involving glycolysis and͞or passage through the pentose phosphate, the Cori cycle and͞or the citrate cycle. The perturbation method described can be adapted to a wide variety of experimental systems and isotope-labeled precursors.…”

“…Naturally occurring glucose consists predominantly of the [U- 12 C 6 ]-isotopolog accounting for Ϸ93 mol %. Each of six molecular species carrying a single 13 C atom accounts for 1.1%. In natural abundance glucose, multiply 13 Clabeled species are rare; for example, the [U- 13 C 6 ]-isotopolog is expected to be present at a level of Ϸ10 Ϫ10 mol %.…”