Question

Why is ATP alone not an effective allosteric regulator of enzyme activity?

Short answer

AMP becomes the allosteric inhibitor in the regulatory enzyme and ATP does not act as allosteric regulator.

Step-by-step solution

Allosteric regulation 

Allosteric regulation occurs when a regulator binds to an enzyme and regulates its activity. An activator or inhibitor can be used as a regulator.

ATP is not an effective allosteric regulator of enzyme activity 

The glycolytic process is allosterically regulated by ATP. In this route, you'll find regulatory enzymes. Hexokinase, phosphofructokinase, and pyruvate kinase are the enzymes that regulate the process.

Phosphofructokinase-1, or PFK-1, is an essential regulator enzyme in this process. Allosteric effectors are present in this enzyme, and ATP competes with AMP for the same allosteric effector site.

Despite the fact that ATP concentrations in cells are higher than AMP concentrations, a little decrease in ATP concentration causes a huge rise in AMP levels.

As a result, AMP becomes the allosteric effector of this key regulating enzyme, whereas ATP alone is ineffective.