Transient isolation of the hexokinase reaction from the glycolytic sequence on initiation of glycolysis in ascites tumor cells

The kinetics of accumulation of glycolytic intermediates during the first 10 sec after glucose addition to Ehrlich ascites tumor cells indicate that hexokinase operates alone for the first 3 sec, utilizing a pre-existing pool of ATP. Between 4 and 5 sec, hexokinase activity declines, while the remainder of the glycolytic sequence begins a coordinated acceleration; after 5 sec, hexokinase activity increases again, following the sharply rising phosphofructokinase activity. The 5 sec point coincides with the minimum ATP level in the cells and also marks the beginning of the coupling between the ATP-utilizing kinases in the head-end of glycolysis and the ATP-generating systems.