Investigations of the mechanisms of glycolytic control during hibernation

Abstract

Molecular mechanisms of glycolytic rate control during hibernation were investigated in the meadow jumping mouse, Zapus hudsonius. The content of fructose-2, 6-bisphosphate, a potent activator of phosphofructokinase, decreased significantly in brain, heart, and fat pad after 5–8 days of hibernation, rose in kidney, and was unchanged in skeletal muscle. Apparent covalent modification of regulatory enzymes of glycolysis during hibernation was examined in brain, heart, kidney, and skeletal muscle but occurred only in selected instances. Hibernation led to a significant reduction in the percentage of glycogen phosphorylase in the phosphorylated a form in brain and produced kinetic changes (altered Ka AMP, I50 citrate) in phosphofructokinase from heart indicative of enzyme covalent modification. No evidence for covalent modification of pyruvate kinase during hibernation was found in any tissue. Covalent modification of enzymes and alterations in fructose-2, 6-bisphosphate content offer organ-specific control over glycolytic rate during hibernation in response to both the general metabolic rate depression of the hibernating state and the individual adjustments in organ fuel use.