D-Fructose-1,6-bisphosphate is an intermediate in carbohydrate metabolism, including glycolysis and gluconeogenesis. During glycolysis, it is generated by the phosphorylation of fructose-6-phosphate by phosphofructokinase. The reverse reaction, mediated by fructose-1,6-bisphosphatase-1, is one of the rate-limiting steps in gluconeogenesis. The same reaction occurs within chloroplasts in plants as part of the reductive pentose phosphate cycle. Because cancer cells adopt glycolysis as a major source of metabolic energy production, this pathway has become a major target for cancer chemotherapy.