Effect of enzyme concentrations on sustained oscillations in the fructose 6-phosphate/fructose 1,6-bisphosphate-cycle.

Sustained oscillations were investigated in an open and homogeneous enzyme system reconstituted from phosphofructokinase, fructose 1,6- biphosphatase , pyruvate kinase, adenylate kinase, and glucose 6-phosphate isomerase. The generation of oscillations if mainly due to antagonistic kinetic effects of AMP on phosphofructokinase and fructose 1,6- biphosphatase under the experimental conditions applied. Sustained oscillations were obtained in a broad range of maximum activities of phosphofructokinase or fructose 1,6- biphosphatase are increased. At low maximum activities of the two enzymes oscillations arise, which form a folded limit cycle, while by increasing concentrations of phosphofructokinase or fructose 1,6-bisphosphatase sustained oscillations are introduced, which are restricted to two dimensions.