Age-linked alterations in fructose-2,6-bisphosphate-induced modulation of rat muscle phosphofructokinase.

Native muscle phosphofructokinase (PFK: EC 2.7.1.11) isolated from 25- and 100-week-old rats was subjected to in vitro studies on fructose-2,6-bisphosphate-induced alterations in the regulatory roles of other key metabolic modulators of this enzyme. Although fructose 2,6-bisphosphate-mediated reversal of citrate inhibition did not show any age-related difference, synergism with glucose-1,6-bisphosphate effect was found to be slightly increased with the enzyme of 100-week-old rats. In addition, apart from a significant decrease in the extent of fructose-2,6-bisphosphate activation, synergism with AMP activation and reversal of ATP and pyridoxal-5-phosphate inhibitions were observed to be decreased markedly with the enzyme of 100-week-old rats in comparison with that of 25-week-old rats. Such age-dependent alterations in muscle PFK provide evidence for conformational modification in this enzyme as a function of age.