Cooperation of fructose-2,6-bisphosphate and AMP in the activation of yeast phosphofructokinase.

Yeast phosphofructokinase is effectively activated by AMP and fructose-2,6-bisphosphate. Both effectors influence the sensitivity of the enzyme with respect to fructose-6-phosphate and increase the respective maximum activities. The dependence of phosphofructokinase activity on the concentration of fructose-2,6-bisphosphate was measured at different AMP concentrations and vice versa. By AMP the half activation constant for fructose-2,6-bisphosphate is decreased by one order of magnitude. The affinity to AMP is significantly increased by fructose-2,6-bisphosphate. AMP increases the maximum activity of the enzyme with respect to fructose-2,6-bisphosphate only slightly, while the maximum activity with respect to AMP is drastically increased by fructose-2,6-bisphosphate. The interaction of the two activators is most pronounced at low levels of fructose-6-phosphate and at high concentrations of ATP.