Increased ATP inhibition of liver phosphofructokinase from genetically diabetic mice

Phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) was partially purified from the livers of genetically diabetic mice (C57BL/KsJ-db) and their lean littermates (C57BL/KsJ). These genetically diabetic mice have been shown to be hyperglucagonemic and to exhibit symptoms resembling those of maturity-onset diabetes in humans. Two isoenzymes of phosphofructokinase were obtained after DEAE-Sephadex chromatography of extracts of livers from either normal or diabetic animals. One of these isozymes, peak II, from the genetically diabetic mice was shown to be more sensitive to ATP inhibition at physiological pH than the peak II isozyme from the normal animals. In addition, the peak II isozyme from the diabetic mice exhibited decreased affinity for fructose 6-phosphate. The altered kinetic properties of phosphofructokinase from diabetic animals are markedly similar to those recently reported for liver phosphofructokinase isolated from normal animals after glucagon treatment. Our results suggest that increased glucagon levels in diabetes may lead to altered regulation of phosphofructokinase in this disease.