Glycogen phosphorylase, liver form (PYGL)

Glycogen phosphorylase, liver form (PYGL), is an allosteric enzyme exclusively expressed in hepatic tissue, where it catalyzes the phosphorolytic cleavage of glycogen to glucose-1-phosphate, representing the rate-limiting step in glycogen catabolism[1][2][6]. The enzyme is a homodimer, requiring pyridoxal phosphate as a cofactor, and is regulated by phosphorylation (via phosphorylase kinase), allosteric effectors (AMP, ATP, glucose), and hormonal signals (glucagon and epinephrine)[2][3]. PYGL is critical for maintaining blood glucose levels during fasting and is implicated in diseases such as glycogen storage disease type VI (Hers disease) and diabetes. Research has identified PYGL as a potential therapeutic target for drugs aiming to reduce hepatic glucose production in diabetes, but enzyme inhibitors must be used cautiously due to the risk of hypoglycemia and interference with normal hepatic metabolic function[2][3][5][6].

Other names

Liver glycogen phosphorylaseGlycogen phosphorylase LPYGL

Inhibition of glycogen phosphorylase reduces hepatic glucose output by blocking the conversion of glycogen to glucose-1-phosphate[2][3]. Enzyme activation by phosphorylation (through glucagon, adrenaline/cAMP signaling); inhibition by allosteric small molecules (e.g., caffeine)[3].