Extended Data Figure 9. FBP is predominantly derived from glucose.

All intact cell experiments in this Figure were performed in the presence of 10% serum. a, Isotopomeric distribution of metabolites derived from D-[U-¹³C]glucose. ¹³C atoms are marked as filled circles. Note that FBP can be converted from various substrates besides glucose, but the conversion of glucose to F6P and then to FBP (grey-shaded area) is the only way that yields completely M+6 labelled FBP. b, c, MEFs (b) or HEK293T cells (c) were incubated in DMEM medium without glucose for 4 h. The medium was then added with 25 mM D-[U-¹³C]glucose. After 15 min or 4 h of incubation, the labeled FBP levels in cells were measured by CE-MS. The results shown that FBP produced after re-addition of glucose to the MEFs was almost entirely M+6 labelled. The experiment was performed twice.