Glukose6phosphat

Glukose6phosphat, commonly known as glucose-6-phosphate (G6P), is a phosphorylated derivative of glucose with a phosphate group on carbon 6. It is formed in the cytosol by the action of hexokinase or glucokinase, which transfer a phosphate from ATP to glucose. G6P is a central metabolite that links multiple pathways in carbohydrate metabolism.

G6P can enter several routes. In glycolysis, it is isomerized to fructose-6-phosphate and then processed to generate ATP and pyruvate. In the liver and kidneys, G6P can be dephosphorylated by the enzyme glucose-6-phosphatase to produce free glucose, which is released into the bloodstream to help maintain blood glucose levels during fasting. This dephosphorylation occurs in the endoplasmic reticulum after transport of G6P into the organelle by the glucose-6-phosphate transporter. G6P also serves as a substrate for the pentose phosphate pathway, yielding NADPH and ribose-5-phosphate, and can feed into glycogen synthesis through conversion to glucose-1-phosphate and UDP-glucose.

Regulation and tissue distribution influence G6P fate. A broad class of tissue hexokinases (I–III) favors glycolysis, while glucokinase in liver and pancreatic beta cells supports glucose storage and metabolic sensing. In the liver, hormonal signals such as insulin and glucagon modulate flux through glycolysis, gluconeogenesis, and glycogen synthesis, coordinating G6P use with whole-body energy status.

Clinical significance includes glucose-6-phosphate dehydrogenase (G6PD) deficiency, which impairs NADPH production in red blood cells and can cause hemolysis under oxidative stress. Defects in glucose-6-phosphatase, the enzyme that converts G6P to glucose, cause glycogen storage disease type I (Von Gierke disease), characterized by severe hypoglycemia and metabolic abnormalities.