91Ó°ÊÓ

The process by which glucose molecule is degraded by the cell to produce energy intermediates such as ATP and NADPH (nicotinamide adenine dinucleotide phosphate) is called glycolysis.Thus, glycolysis is the process by which the body obtains energy from glucose.

In glycolysis, PFK catalyzes the synthesis of fructose-1,6-biphosphate from fructose-6-phosphate.It utilizes ATP for the phosphorylation of fructose-6-phosphate.

From the graph, it can be inferred that the slope under low ATP concentration is very steep and reaches its peak quickly. On the contrary, the slope at high ATP concentration is not very steep and reaches its peak much laterthan the slope at low ATP concentration.

This exhibits that phosphofructokinase is more active under low ATP concentration as compared to high ATP concentration.

PFK is a key regulatory enzyme of the glycolysis pathway. Increased levels of ATP concentration allosterically inhibit the enzyme. This means ATP inhibits the affinity of PFK for fructose-6-phosphate. As a result, the activity of PFK decreases in the presence of high ATP concentration.

On the other hand, the enzyme is stimulated at a high AMP (adenosine monophosphate)/ low ATP concentration.This means the low ATP concentration increase the affinity of the enzyme for the substrate.As a result, the activity of the enzyme increases in the presence of low ATP concentration.

ATP is an allosteric inhibitor for PFK. A high level of ATP indicates that the cell has a high concentration of ATP and, thus, glycolysis that produces energy (ATP) is not required by the cell.Thus, high ATP concentration inhibits the activity of PFK.

On the contrary, a low concentration of ATP indicates that the energy is required by the cell, so glycolysis is stimulated. Thus, low ATP concentration activates the PFK.

Therefore, the allosteric inhibitor of PFK by ATP signals that energy is not required by the cell, thereby inhibiting glycolysis.