Solutions For An Introduction to Medicinal Chemistry Chapter 5 Problem 5Q

The pathway mentioned below describes the cascade of steps involved in the regulation of Glycogen.

Figure: Regulation of glycogen synthesis and metabolism in liver cell.

The cAMP is hydrolysed to AMP with the help of enzyme cAMP phosphodiesterase. In the regulation of glycogen synthase and glycogen phosphorylase, adrenaline is the initial hormone which initiates the signaling at β-adrenoreceptors. This leads to synthesis of cAMP and pyrophosphate from ATP with the action of enzyme ‘Adenylate cyclase’.

The cAMP activates the Protein kinase A (PKA) enzyme. This further leads to phosphorylation of three enzymes namely phosphorylase kinase, glycogen synthase and phosphorylase inhibitor molecule by the catalytic subunit of enzyme PKA.

The inhibitor of the enzyme cAMP phosphodiesterase prevents the conversion of cAMP to ATP on its hydrolysis. Hence, this stimulates the activity of Protein kinase A which in turn, favors glycogenolysis that is breakdown of glycogen to glucose-1-phosphate.