Interaction of ADP and fructose-2,6-bisphosphate with phosphofructokinase-1 from yeast.

ADP was found to activate or, depending on the experimental conditions, to inhibit yeast phosphofructokinase-1. In the absence of AMP and fructose-2,6-bisphosphate ADP increases the apparent affinity of the enzyme to fructose-6-phosphate. At low ATP concentrations the maximum activity with respect to fructose-6-phosphate decreases in the presence of ADP, while at high ATP a significant increase of the maximum activity by ADP is observed. In the presence of fructose-2,6-bisphosphate and AMP only the inhibiting effect of ADP persists. The data may be interpreted in terms of a hyperbolic inhibition mechanism.