AGL (amylo-alpha-1,6-glucosidase and 4-alpha-glucanotransferase) is a multifunctional enzyme that acts as both a 1,4-alpha-D-glucan:1,4-alpha-D-glucan 4-alpha-D-glycosyltransferase and amylo-1,6-glucosidase in glycogen degradation 1. The gene spans 85 kb on chromosome 1, containing 35 exons that encode a 7.0-kb mRNA producing 1532 amino acids 1. AGL exhibits tissue-specific expression through at least two promoter regions: the major isoform is widely expressed in liver and muscle, while muscle-specific isoforms are driven by an alternative promoter 1. Genetic deficiency of AGL causes glycogen storage disease type III (GSD-III), a disorder of glycogen metabolism characterized by impaired glycogen breakdown 1. Loss of AGL function in bladder cancer cells impairs normal glycogen metabolism, decreasing cellular glycogen storage and increasing lactate production, while simultaneously elevating serine-to-glycine conversion through SHMT2 upregulation, which promotes nucleotide synthesis and cell proliferation 2. This metabolic reprogramming represents a key mechanism in bladder tumorigenesis. Understanding AGL's critical role in glycogen homeostasis and its dysregulation in disease provides important insights for developing targeted therapeutic strategies for both genetic glycogen storage disorders and metabolic complications in cancer.