GlgC

GlgC is the gene that encodes the enzyme ADP-glucose pyrophosphorylase (AGPase) in many bacteria. The enzyme catalyzes the first committed step in glycogen and other α-glucan biosynthesis by converting glucose-1-phosphate and ATP into ADP-glucose and pyrophosphate. ADP-glucose then serves as the glucosyl donor for glycogen synthase (GlgA) and related glucosyltransferases, enabling the elongation and branching of glycogen.

Genomic and functional context varies across species. In Escherichia coli and many other bacteria, glgC is the gene responsible for producing AGPase and is generally expressed as a cytosolic enzyme that forms a functional oligomer. In some organisms, AGPase activity is more complex and can involve regulatory subunits or additional subunit architecture, reflecting a broader evolutionary relationship to the plant-type AGPase that operates as a heteromer.

Regulation and structure are tied to cellular metabolic state. glgC is typically located within operons and regulatory networks governing glycogen metabolism, often near genes such as glgA (glycogen synthase) and glgB (branching enzyme). Enzyme activity is modulated by metabolites that reflect carbon and energy status; activators indicate a favorable carbon supply, while inhibitors reflect energy stress or resource limitation. The enzyme is usually cytosolic and forms oligomeric assemblies that enable responsive control of ADP-glucose production.

Importance and applications. Glycogen storage controlled by GlgC influences a cell’s ability to cope with nutrient fluctuations and stress, contributing to survival in variable environments. In research and biotechnology, altering GlgC activity can modify glycogen content and impact studies of carbon storage, metabolism, and persistence in certain bacterial pathogens.