Figure 4

PFK activity measured in c4 and WT cells and tumours under optimal conditions and those prevailing in vivo. PFK activity (nmol/mg protein/min) measured either under optimal conditions (1 mM ATP, 2 mM AMP) or under the conditions prevailing in vivo (0.7 mM ATP and 0.25 mM AMP for c4; 1 mM ATP and 0.04 mM AMP for WT). No significant difference in PFK activity was seen when measured under optimal conditions comparing WT and c4 tumours or cells (p > 0.1). However, under conditions prevailing in vivo, PFK activity was significantly higher in c4 than in WT cells or tumours (p < 0.005).