Fig. 1.

Serine increases PKM2 activity and glycolytic rate. (A) In vitro PKM2 activity increases in the presence of serine. Assay performed with a series of serine concentrations as indicated with and without 10 μM FBP (data represent mean ± SEM, n = 3). (B) Equal numbers of H1299 cells were incubated with various concentrations of serine for 16 h, cells were trypsinized, stained with Trypan blue, and counted (data represent mean ± SEM, n = 3). (C) Glucose consumption and lactate production in B were measured as described in Materials and Methods and normalized to cell number (data represent mean ± SEM, n = 3). (D) The lactate production/glucose consumption ratio increases with the serine concentration (data represent mean ± SEM, n = 3).