Glycogen debranching enzyme (AGL) (AGL)

Glycogen debranching enzyme (AGL) is a large, multifunctional protein essential for the mobilization of glucose from glycogen stores (UniProt P35573). It possesses two distinct enzymatic activities: 4-alpha-glucanotransferase and amylo-alpha-1,6-glucosidase, which work together to bypass the branch points in glycogen that glycogen phosphorylase cannot process (PubMed: 25559920). Deficiencies in AGL lead to Glycogen Storage Disease Type III (GSD III), also known as Cori or Forbes disease, which is characterized by the accumulation of limit dextrin-like glycogen in the liver, heart, and skeletal muscles (NIH: Genetic and Rare Diseases Information Center). This accumulation results in clinical manifestations such as severe hypoglycemia, hepatomegaly, growth retardation, and progressive myopathy or cardiomyopathy. Current therapeutic strategies focus on restoring AGL expression through mRNA-based therapies, such as mRNA-3630, or viral-mediated gene replacement to normalize glycogen metabolism and prevent organ damage (Moderna; AskBio). These therapies aim to provide a functional version of the enzyme to tissues that lack it, thereby enabling the breakdown of stored glycogen and maintaining glucose homeostasis. Clinical trials are investigating the safety and efficacy of these approaches in patients with GSD III to address the underlying metabolic defect.

Other names

Amylo-alpha-1,6-glucosidase4-alpha-glucanotransferaseGDEAmylo-1,6-glucosidase,4-alpha-glucanotransferaseGSD3GDE1

mRNA-mediated protein replacement therapy and AAV-mediated gene replacement therapy aim to restore functional glycogen debranching enzyme activity in affected tissues.