Question: Step 3 in Figure 9.9 is a significant point of regulation of glycolysis. ATP and related molecules allosterically regulate the enzyme phosphofructokinase (see Concept 8.5). Considering the overall result of glycolysis, would you expect ATP to inhibit or stimulate the activity of this enzyme? Explain. (Hint: Make sure you consider the role of ATP as an allosteric regulator, not as a substrate of the enzyme.)

Glycolysis is the process of breaking the glucose molecules resulting in the formation of pyruvate molecules. This molecule then enters another process of aerobic respiration or anaerobic fermentation. The other products produced along with the pyruvate molecules are ATP.

The enzyme that belongs to the category of kinase mediates the phosphorylation of fructose-6-phosphate. It is one of the critical steps in glycolysis that results in the formation of fructose 1,6 bisphosphate.

The main work of phosphofructokinase is to transfer the phosphate group present in the ATP molecules to the other end of glucose. The increasing level of ATP results in the allosteric regulation of enzyme ATP.

The effector molecules produced in the process, in turn, inhibit the enzyme involved in the particular reaction, are known as allosteric inhibitors. In this process, ATP is the effector molecule that acts as an allosteric inhibitor of phosphofructokinase.

Hence, ATP is the energy molecule produced in the glycolysis process, acting as an allosteric inhibitor of the phosphofructokinase enzyme.