Glycolysis is a catabolic pathway in which the six-carbon molecule (glucose) is changed into the three-carbon molecule (pyruvic acid). In the third step of glycolysis, fructose-6-phosphate gets converted into fructose-1,6-bisphosphate by the enzyme phosphofructokinase. The rate of glycolysis is regulated by the enzyme phosphofructokinase. It is an allosteric enzyme, and excess ATP causes allosteric inhibition. A high level of ATP and citric acid decreases the affinity of enzyme for fructose 6-phosphate. This is because the process of glycolysis and TCA cycle is to produce ATP, but when ATP is in abundance then the need for the process to produce ATP becomes less significant.