Glycogenesis inhibition

Not only is phosphorylase activated by a rise in concentration of cAMP (via phosphorylase kinase), but glycogen synthase is at the same time converted to the inactive form both effects are mediated via cAMP-dependent protein kinase. Thus, inhibition of glycogenolysis enhances net glycogenesis, and inhibition of glycogenesis enhances net glycogenolysis. Furthermore,... 

Figure 18-8. Coordinated control of glycogenolysis and glycogenesis by cAMP-dependent protein kinase. The reactions that lead to glycogenolysis as a result of an increase in cAMP concentrations are shown with bold arrows, and those that are inhibited by activation of protein phosphatase-1 are shown as broken arrows. The reverse occurs when cAMP concentrations decrease as a result of phosphodiesterase activity, leading to glycogenesis.

Raz I> Katz A, Spencer MK Epinephrine inhibits insulin-mediated glycogenesis but enhances glycolysis in human skeletal muscle. Am J Physiol 1991 260 E430. 

Vanden Bossche and de Nollin and others [12-14] have shown that benzimidazole carbamates, such as mebendazole, inhibit glucose uptake by helminths in vivo and in vitro-, this enhances endogenous glycogen utilization and is accompanied by reduction in glycogenesis. 

The glycogenesis and glycogenolysis enzymes subject to hormonal control are glycogen synthase and phosphorylase, respectively. Briefly, glycogen synthase is inhibited by high cellular cAMP and Ca2+ levels, whereas phorphorylase is stimulated. The mechanisms for accomplishing this are quite complex. 

When occupied, the insulin receptor becomes an active tyrosine kinase enzyme that causes a phosphorylation cascade that ultimately has the opposite effect of the glucagon/cAMP system the enzymes of glycogenolysis are inhibited and the enzymes of glycogenesis are activated. Insulin also increases the rate of glucose uptake into several types of target cells, but not liver or brain cells. 

---