Activity and kinetics of liver 6-phosphofructokinase in normal and diabetic rats

The activity and kinetics of phosphofructokinase were measured in the postmicrosomal supernatant of livers removed from either normal or streptozotocin-induced diabetic rats. The activity of the enzyme was lower in diabetic than normal rats. However, the relative magnitude of changes in reaction velocity evoked by different concentrations of D-fructose 6-phosphate, ATP, D-glucose 1,6-bisphosphate and/or D-fructose 2,6-bisphosphate were comparable in normal and diabetic rats. Such was also the case after separation of cytosolic proteins from low molecular weight metabolites by gel filtration chromatography. These findings suggest that a sustained increase in intracellular D-glucose concentration, as presumably occurring in hepatocytes of diabetic animals, does not result in any obvious alteration of the intrinsic kinetic properties of phosphofructokinase.