PYGM

PYGM is the official gene symbol for the human gene that encodes the muscle form of glycogen phosphorylase. This enzyme catalyzes the terminal step of glycogenolysis in skeletal muscle, releasing glucose-1-phosphate from glycogen to provide a rapid source of glucose for energy during muscle activity.

The PYGM gene is predominantly expressed in skeletal muscle and, to a lesser extent, in other tissues. The muscle glycogen phosphorylase protein functions as part of the glycogen metabolic pathway and is regulated by energy status, allosteric effectors, and phosphorylation. It plays a critical role in mobilizing glycogen stores during exercise and during periods of increased energy demand in muscle tissue.

Clinical relevance is most prominently seen in McArdle disease, or glycogen storage disease type V, which results from pathogenic variants in PYGM. Individuals with this condition typically experience exercise-induced muscle pain, cramps, and fatigue, with possible myoglobinuria after strenuous activity. The disorder is inherited in an autosomal recessive manner. Diagnosis is supported by genetic testing for PYGM mutations and by biochemical assays showing reduced or absent muscle glycogen phosphorylase activity. Management focuses on symptom relief and lifestyle adjustments, including tailored exercise programs and nutritional strategies to mitigate fatigue.

In research and medical genetics, PYGM is used as a standard symbol in human genomics and comparative studies of glycogen metabolism. The gene is conserved across many species, reflecting the evolutionary importance of glycogen utilization in muscle energy production.