Category: biosynthesis
Glycogen synthesis (glycogenesis): G6P → G1P (phosphoglucomutase) → UDP-glucose (UDP-glucose pyrophosphorylase) → glycogen extension by glycogen synthase. Glycogen breakdown (glycogenolysis): glycogen phosphorylase → G1P → G6P → fates. Liver glycogen feeds blood glucose; muscle glycogen feeds local glycolysis only (no G6Pase). Glycogen storage diseases: von Gierke (G6Pase, type I), Pompe (acid maltase, type II — only one affecting lysosomal glycogen), McArdle (muscle phosphorylase, type V). Regulation: glucagon + epinephrine activate phosphorylase via PKA cascade; insulin activates glycogen synthase via PP1.