What does Substance A function as?

The correct answer to this question is An allosteric inhibitor. Related to biochemistry, allosteric inhibition happens when the binding of one ligand makes the affinity for substrate decrease at other active sites. Also known as harmful allosteric modulation, allosteric inhibitors are used as anticoagulants.

An example of an allosteric inhibitor is strychnine. This is a convulsant poison. Strychnines act as allosteric inhibitors of the glycine receptors. Another example of these inhibitors is the relationship between phosphofructokinase, which is an enzyme, and ATP. Phosphofructokinase, also known as PFK, start the third step of glycolysis and they inhibit high levels of ATP in a cell.

Allosteric inhibition is the progression by which a regulatory molecule attaches to an enzyme in a spot different from the active site for an additional particle, which causes a conformational alteration in the dynamic place for the second molecule, thwarting binding.

This progression is also known as noncompetitive inhibition. A similar method is used in allosteric activation, in which the modification of the binding site increases the binding of the second molecule, which is referred to as noncompetitive initiation.

In a method similar to allosteric inhibition, competitive inhibition is also used to prevent enzymatic activation. In competitive inhibition, the controlling molecule binds to the same site as the other molecule, which hinders binding from occurring.