Question

Explain the role of the allosteric site in enzyme inhibition.

Answer 1

Hint: Allosteric Inhibition takes place when an inhibitor binds to the allosteric site of an enzyme. The word “Allo” means other and “steric” means site. So, the allosteric site is different from the active site of the enzyme molecule.

Complete answer:
Enzymes are protein molecules that act as the biological catalyst which increases the rate of the reaction and is present in the body of all living organisms. Almost all biochemical reactions whether it is gene formation, hormone secretion, or metabolism inside our body need an enzyme as a catalyst to regulate and control proper development.
Enzymes have many receptor sites on their surface which receive and bind to substrate molecules that bring conformational changes in the enzyme-producing a physiological effect or change in the functioning of cells. These receiving sites are also known as active sites of the enzyme.

The sites present on enzymes other than the active sites on which some other kinds of substances bind are known as allosteric sites. The substances which bind to allosteric sites influence the activity of that enzyme. They can either activate or inhibit the action of an enzyme.
The inhibition of enzyme refers to the decrease in the activity or affinity of the enzyme towards the substrate. It happens when a molecule other than a substrate molecule blocks the active site of the enzyme by binding to it.
Allosteric inhibition- When the inhibition of enzyme activity takes place due to the binding of a molecule on an allosteric site of the enzyme, it brings a change in the shape of the enzyme such that its active site becomes unfit to make a complex with the substrate. Hence, the enzyme activity decreases and this results in enzyme inhibition. It can be visualized as represented below:

Thus, in this way, the presence of an allosteric site can cause inhibition of the enzyme.

Note:
The presence of an allosteric site in the enzyme can either or activate or inhibit the enzyme depending upon the nature of the molecule binding to the allosteric site. We have already discussed how allosteric inhibition takes place. In the case of allosteric activation, a molecule binds to a site other than an active site and brings a change in a way that increases the affinity of the enzyme to get bound to its substrate.
A substrate is a starting material that initiates a chemical reaction.