The Purine Nucleotide Cycle

Abstract

The oscillations observed previously in the operation of the purine nucleotide cycle correspond to oscillations in the glycolytic pathway, as shown by metabolite assays. The oscillatory process involves the activation of phosphofructokinase by its product fructose diphosphate, as well as control by the adenine mononucleotides. The changes in the concentrations of ATP, ADP, and AMP associated with the glycolytic oscillations, and the corresponding changes in the concentrations of GTP and GDP, account for the behavior of the purine nucleotide cycle. The responsiveness of the purine nucleotide cycle to changes in the [ATP]:[ADP] ratio is consistent with its proposed role in maintaining a high [ATP]:[ADP] ratio in the face of a high rate of ATP usage during muscular contraction.