The effect of Mg2+ upon 6-phosphofructokinase activity in Ehrlich ascites tumor cells in vivo

The effect of Mg2+ addition to intact Ehrlich ascites tumor cells (EATC) has been investigated. A decrease of glucose 6-phosphate (G6P) content and an increase of fructose 1,6-diphosphate (FDP) content are detected in glucose utilizing EATC incubated with increasing Mg2+ concentrations (from 0 to 5.0 mM). The strong enhancement of FDP/G6P ratio is taken as evidence for in vivo stimulation of phosphofructokinase 1 (PFK) (ATP:D-fructose-6-phosphate 1-phosphotransferase; EC 2.7.1.11). A similar effect can be observed when glucose is replaced by fructose as the glycolytic substrate. Stimulation of PFK is paralleled by substantial depletion of ATP. Cytochalasin B prevents the observed phenomena. Cell total Mg increases by about 15% when EATC are incubated with 5 mM Mg2+. The overall data show that extracellular Mg2+ may modulate glycolytic flux in EATC in vivo. Implications and significance of these phenomena in the regulation of cancer cell metabolic features are discussed.