Glucose16bisphosphate

Glucose-1,6-bisphosphate (G16BP) is an intermediate metabolite in carbohydrate metabolism. It is a phosphorylated form of glucose, meaning a phosphate group is attached to the carbon atom at position 1 and another at position 6. This molecule plays a role in several biochemical pathways, particularly in glycolysis and gluconeogenesis.

The interconversion of glucose-6-phosphate (G6P) and glucose-1-phosphate (G1P) is catalyzed by phosphoglucomutase. G1P is then further phosphorylated to G16BP by phosphoglucokinase. This latter reaction is often considered a regulatory step in glycolysis. G16BP itself is not directly metabolized further in large quantities but rather acts as a substrate or regulator for other enzymes.

One of its key functions is as a substrate for the enzyme phosphoglucan phosphatase, which can dephosphorylate G16BP to G6P, effectively returning it to the main glycolytic pathway. G16BP also has a significant regulatory role. It can act as an allosteric activator for enzymes like phosphofructokinase-1, a crucial regulatory enzyme in glycolysis. Conversely, it can inhibit fructose-1,6-bisphosphatase, an enzyme involved in gluconeogenesis. This dual regulatory action helps to coordinate the balance between glucose breakdown and synthesis. The concentration of G16BP is tightly controlled within cells, reflecting the metabolic state and energy demands.