Which enzyme does fructose 2,6-bisphosphate inhibit?

Fructose 2,6-bisphosphate plays a crucial role in the regulation of glucose metabolism, particularly by affecting key enzymes in the glycolytic and gluconeogenic pathways. It acts as a potent inhibitor of FBPase-1 (fructose 1,6-bisphosphatase), which is an important enzyme in gluconeogenesis—the process of producing glucose from non-carbohydrate sources.

The inhibition of FBPase-1 by fructose 2,6-bisphosphate serves to decrease the conversion of fructose 1,6-bisphosphate to fructose 6-phosphate, thereby slowing down gluconeogenesis. This is strategically important because when cellular energy or glucose levels are high, glycolysis (the breakdown of glucose) should be favored over gluconeogenesis. By inhibiting FBPase-1, fructose 2,6-bisphosphate promotes the use of glucose through glycolysis while simultaneously preventing the production of glucose, helping to maintain metabolic balance.

In addition to this inhibitory action, fructose 2,6-bisphosphate also activates PFK-1 (phosphofructokinase-1), another key regulatory enzyme that promotes glycolysis. This