Fig. 1

Example complex metabolite UDP-GlcNAc and associated expert-derived moiety model. a Major human metabolic pathways leading from glucose to the four moieties of UDP-GlcNAc. b The representative moiety model is based on the expected metabolic tracing from ¹³C-labeled glucose to UDP-GlcNAc, with the exception of one carbon in the uracil moiety that traces from carbon dioxide. The moiety states variables are identified by a lowercase moiety letter followed by a number representing the ¹³C isotope content. The moiety state variables (model parameters) are used to calculate specific components of the relative isotopologue intensity