Question

Phosphofructokinase is the main regulatory enzyme of glycolysis

Answer 1

Phosphofructokinase (PFK) is able to regulate glycolysis through allosteric inhibition, and in this way,the cell increase or decrease the rate of glycosis is responsible to the cell's energy requirements.
For example: a high ratio of ATP to ADP will inhibit PFK and glycolysis.

Answer 2

Phosphofructokinase is the most prominent regulatory enzyme in glycolysis, but it is not the only one. Hexokinase, theenzyme catalyzing the first step ofglycolysis, is inhibited by its product, glucose 6-phosphate. ... For example, whenphosphofructokinase is inactive, the concentration of fructose 6-phosphate rises.