phosphoglucose

Phosphoglucose refers to glucose phosphate esters, molecules in which a phosphate group is covalently bound to glucose. The most common forms are glucose-6-phosphate (G6P) and glucose-1-phosphate (G1P). In physiological conditions, the phosphate is attached to carbon 6 or carbon 1 of the glucose molecule, imparting a negative charge that prevents diffusion across membranes.

Glucose-6-phosphate is a central metabolite in energy metabolism. It is produced from glucose by the enzymes hexokinase or glucokinase (liver and pancreatic cells) using ATP. G6P can be isomerized by phosphoglucose isomerase to fructose-6-phosphate, entering glycolysis. It can also be diverted into the pentose phosphate pathway via glucose-6-phosphate dehydrogenase, generating NADPH and ribose-5-phosphate. In liver and kidney, G6P can be dephosphorylated by glucose-6-phosphatase to release free glucose, a step important for maintaining blood glucose levels.

Glucose-1-phosphate arises mainly from glycogen breakdown. Glycogen phosphorylase releases G1P, which is converted to G6P by phosphoglucomutase. G6P from glycogen can then enter glycolysis or be used to synthesize UDP-glucose for glycogen synthesis. The flow of G1P thus links glycogen metabolism to broader carbohydrate fluxes.

Phosphoglucose-related metabolism is conserved across many organisms and cell types and involves a network of enzymes that regulate the balance between energy production, storage, and biosynthesis. Disruptions in these pathways can affect glucose homeostasis and cellular energy metabolism.