Regulation of glycogenolysis in the locust fat body during flight

Abstract

Glycogen reserves in the fat body of Locusta migratoria decrease dramatically during the first two hours of flight. In fat body of rested locusts only 10% of glycogen phosphorylase occurs in the active form. The enzyme is activated significantly during flight, when up to one-third of the total phosphorylase becomes active. Phosphorylase activation can also be accomplished by injection of corpus cardiacum extracts, to give a maximum of circa 75% active enzyme. Locust fat body is shown to contain protein kinase activity, which can be activated both by cyclic AMP and cyclic GMP. Apparent Ka-values are 0.13μM for cyclic AMP and 0.16 μM for cyclic GMP. Results are discussed in relation to regulation of substrate utilization during flight.