What happens to the activity of phosphofructokinase (PFK) when ATP levels are high?

Phosphofructokinase (PFK) is a key regulatory enzyme in the glycolytic pathway, primarily tasked with converting fructose-6-phosphate to fructose-1,6-bisphosphate. The activity of PFK is tightly regulated by the energy status of the cell, particularly by the levels of ATP.

When ATP levels are high, this indicates that the cell has sufficient energy. In this state, the enzyme is inhibited. This inhibition serves to prevent the unnecessary processing of glucose through glycolysis when energy supply is adequate, thereby conserving resources and maintaining metabolic balance. High ATP levels signal to the cell that it does not need to produce more energy, leading to reduced PFK activity as a means to slow down glycolysis.

This feedback mechanism is crucial, as it allows the cell to adjust its metabolism according to energy demands. If ATP levels drop, signaling a need for more energy, PFK activity would increase to enhance glycolysis and facilitate ATP production. The regulation of PFK by ATP exemplifies the intricate control exerted over metabolic pathways in response to the cell's needs.