| Comments |
P.6 left column bottom paragraph: "The textbook view involves three strongly
thermodynamically forward-driven reactions, which cannot reverse flux direction during gluconeogenesis and thus must be bypassed, linked by near-equilibrium ones that, during gluconeogenesis, flip their direction of net flux (Fig. 4b). The three committed reactions are glucose phosphorylation (hexokinase in yeast and in mammals and phosphotransferase system in E. coli), phosphofructokinase and pyruvate kinase. Glucose phosphorylation was omitted from [investigators'] analysis because of [their] inability to
quantify the intracellular glucose concentration (given the abundance of media glucose). For phosphofructokinase and pyruvate kinase, [they] found that the former is substantially more forward driven: ΔG for phosphofructokinase ranges from −13 kJ/mol to −25 kJ/mol, which results in minimal back flux (<0.7% of forward flux), whereas for pyruvate kinase, it ranges from approximately −4 kJ/mol to −10 kJ/mol, resulting in 2% to 20% backward-to-forward flux." Investigators studied E. coli, yeast, and mammalian cell line iBMK. iBMK=Immortalized Baby Mouse Kidney Epithelial Cells |