Fructose16bisphosphate

Fructose-1,6-bisphosphate, commonly abbreviated as FBP, is a phosphorylated sugar intermediate in glycolysis. It is formed in the cytosol by the phosphorylation of fructose-6-phosphate (F6P) by phosphofructokinase-1 (PFK-1) using ATP, representing a key committed step in glycolytic metabolism.

FBP is then cleaved by the enzyme aldolase into glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP). DHAP can be isomerized to G3P, and the two triose phosphates continue through glycolysis to generate energy-rich intermediates and pyruvate.

Regulation of the formation and metabolism of FBP is a major control point in glycolysis. PFK-1 activity responds to the cell’s energy state, with activators such as AMP and fructose-2,6-bisphosphate (a potent activator of PFK-1) and inhibitors including ATP, citrate, and low pH. This regulation links carbohydrate availability to the rate of glycolytic flux.

Role in gluconeogenesis: in the gluconeogenic pathway, fructose-1,6-bisphosphate is dephosphorylated by fructose-1,6-bisphosphatase to yield fructose-6-phosphate, bypassing the PFK-1 checkpoint and enabling glucose synthesis when energy or biosynthetic needs require it.

Fructose-1,6-bisphosphate is a fundamental metabolite studied to understand glycolysis and its regulation. Errors in its production or handling can impact cellular energy production and metabolic balance.