The role of fructose 2,6-bisphosphate in the long-term control of phosphofructokinase in rat liver

The phosphofructokinase stabilizing factor, believed to be a peptide of molecular weight 3,800 (Dunaway G.A. and Segal H.L., 1976, J. Biol. Chem. 251, 2323-2329), shares many chemical and biological properties with fructose 2,6-bisphosphate. It co-migrated with it upon gel filtration in the molecular weight range 300-400 or 3,000-4,000 depending upon the ionic strength of the solution. Fructose 2,6-bisphosphate is the most potent phosphofructokinase stabilizing agent present in the liver of a fed rat. Its disappearance during fasting and diabetes could account for the faster rate of degradation of phosphofructokinase reported to occur under these conditions. The effect of starvation to decrease by 60% the phosphofructokinase content of the liver is, however, for its greatest part, related to a non-specific decrease in liver mass.