Figure 1

Glycogen metabolism and glycolysis pathway. (a) Enzymes involved in glycogen metabolism and the glycolysis pathway are listed using Roman numerals. They are categorized into glycogen storage diseases (GSD) types 0 and I–XIV, presented as liver form, muscle form, or both. (b) Phosphorylase kinase deficiency causes GSD IX. The enzyme comprises four copies of each of four subunits: α, β, γ, and δ. The schematic figure shows subunit function and the genes that cause liver or muscle forms of GSD IX.