Oscillations in the phosphofructokinase--fructose 1,6-bisphosphatase cycle. II. Influence of fructose 1,6-bisphosphatase on the character of oscillatory states.

The dynamic behaviour of an open futile cycle composed of phosphofructokinase and fructose 1,6-bisphosphatase has been investigated in a homogeneous reconstituted enzyme system in which the two enzymes cooperate with pyruvate kinase, adenylate kinase and glucose 6-phosphate isomerase. By the kinetic cooperation of phosphofructokinase and fructose 1,6-bisphosphatase various types of dynamic patterns can be generated. In the absence of fructose 1,6-bisphosphatase oscillations do not occur. As experimentally demonstrated, in a definite region of maximum activities of fructose 1,6-bisphosphatase sustained oscillations originate while at higher concentrations of the enzyme damped oscillations appear. At increasing concentrations of fructose 1,6-bisphosphatase damping is strengthened. Finally, at very high concentrations of fructose 1,6-bisphosphatase the metabolites relax monotonously to the stationary states. The observed oscillatory phenomena are mainly caused by the antagonistic effects of AMP on the kinetics of phosphofructokinase and fructose 1,6-bisphosphatase.