PHKG1 encodes the gamma catalytic subunit of phosphorylase kinase (PhK), a key regulatory enzyme in glycogen metabolism that mediates neural and hormonal control of glycogenolysis by phosphorylating and activating glycogen phosphorylase 1. The enzyme is expressed in multiple tissues including muscle, liver, brain, heart, and tongue, with evidence of extensive transcriptional processing including an alternate intronic polyadenylation site that produces a truncated protein variant 2. Beyond its classical role in glycogen metabolism, PHKG1 has emerging significance in cancer biology, where it promotes tumor metastasis through enhanced glycogenolysis via the PI3K/AKT pathway, particularly in lung adenocarcinoma 3. The gene also functions in angiogenesis, with its upregulation observed in human tumor samples and copy number aberrations being common features in various cancers 4. In glycogen storage disease type IX, mutations in PHKG1 cause phosphorylase kinase deficiency, though these account for only a minority of cases with muscle glycogenosis and low PhK activity 5. Additionally, PHKG1 expression is downregulated in response to glycogen synthase deficiency, indicating its role in maintaining metabolic homeostasis 6.