Stable Isotope-Assisted Metabolomics for Network-Wide Metabolic Pathway Elucidation

The combination of high-resolution LC–MS-based
untargeted
metabolomics with stable isotope tracing provides a global overview
of the cellular fate of precursor metabolites. This methodology enables
detection of putative metabolites from biological samples and simultaneous
quantification of the pattern and extent of isotope labeling. Labeling
of Trypanosoma brucei cell cultures with 50% uniformly 13C-labeled glucose demonstrated incorporation of glucose-derived
carbon into 187 of 588 putatively identified metabolites in diverse
pathways including carbohydrate, nucleotide, lipid, and amino acid
metabolism. Labeling patterns confirmed the metabolic pathways responsible
for the biosynthesis of many detected metabolites, and labeling was
detected in unexpected metabolites, including two higher sugar phosphates
annotated as octulose phosphate and nonulose phosphate. This untargeted
approach to stable isotope tracing facilitates the biochemical analysis
of known pathways and yields rapid identification of previously unexplored
areas of metabolism.