Fig. 5.

Metabolite labelling experiments and flux balance analyses support the Reversed NOPPP model. (A) [1-¹³C]-glucose metabolism leads to unlabelled S7P when S7P is made via the PPP alone, as the first carbon is lost as carbon dioxide in the oxidative PPP. A small proportion of [1-¹³C]-S7P could be detected through the S7P-producing reaction of Shb17 (pink). (B) Flux through glycolysis to S7P via the Reversed NOPPP reaction can be measured using [1-¹³C]-glucose. [1-¹³C]-glucose leads to [1-¹³C]-S7P when S7P is produced via the glycolytic and Reversed NOPPP routes. (C) The proportion of [1-¹³C]-G6P, [1-¹³C]-F6P and [1-¹³C]-S7P of the total amount of each metabolite detected is shown, where m/z 259 -> 199, m/z 259 -> 169 and m/z 289 -> 97 were analyzed respectively. The fragmentation patterns used for these compounds can be found in Additional File 1: Figure S10. The carbon flux through the glycolytic/Reversed NOPPP route is calculated based on the proportion of labelled [1-¹³C]-S7P among the total amount of S7P detected. Error bars represent the standard deviation (SD) of three independent experiments. Significance was determined using an unpaired t-test. ** p < 0.01, *** p < 0.001. (D) The effect of PFK deletion on fluxes through key glycolytic and PPP reactions, as demonstrated in an enzyme-constrained model. The wild-type and PFK-knockout flux values are depicted in brown and dark green respectively