Final answer:
Inhibition of phosphofructokinase leads to accumulation of fructose-6-phosphate and glucose-6-phosphate due to the halt in the glycolytic flux, as this enzyme is rate-limiting in glycolysis.
Step-by-step explanation:
If phosphofructokinase is inhibited, the upstream molecules of fructose-6-phosphate (F-6-P) and glucose-6-phosphate (G-6-P) accumulate in the cell. Phosphofructokinase is a rate-limiting enzyme in the glycolytic pathway, meaning it plays a critical role in regulating the speed of the pathway.
When this enzyme is inhibited, the phosphorylation of F-6-P to fructose-1,6-bisphosphate cannot occur, causing a buildup of F-6-P and its precursor, G-6-P. This inhibition can result from high levels of ATP, which signals that the cell currently has enough energy and does not need to continue with energy production through glycolysis. Consequently, phosphofructokinase activity decreases due to end product inhibition, and the glycolytic flux slows down or stops, leading to increased concentrations of the upstream metabolites.