Glycogen phosphorylase, liver form

Glycogen phosphorylase, liver form (PYGL) is an allosteric enzyme catalyzing the phosphorolytic cleavage of glycogen to glucose-1-phosphate, a rate-limiting step in glycogen catabolism essential for cellular and organismal glucose homeostasis (UniProt: P06737). The protein is predominantly expressed in hepatic tissue where it plays a central regulatory role in energy metabolism.

PYGL is associated with Glycogen Storage Disease 6 (GSD6, MIM 232700), a metabolic disorder characterized by mild to moderate hypoglycemia, mild ketosis, growth retardation, and hepatomegaly, though cardiac and skeletal muscle are typically spared (UniProt: P06737).

In Alzheimer's Disease, PYGL is significantly upregulated in post-mortem AD brain tissue relative to age-matched controls (Chaparral AD proteomics). Quantitative proteomics analysis detected a mean log2 fold-change of 0.61 across examined subcellular fractions, suggesting increased glycogen metabolism-related enzymatic activity in AD brain pathology.