In all living systems, the biochemical reactions are catalysed by enzymes. Hence, these enzyme actions are highly essential for the normal functioning of the system. If their normal enzyme activity is inhibited, then the system will be affected. This principle is usually applied to kill many pathogens.
In enzyme catalysed reactions, the substrate molecule binds to the active site of the enzyme by means of the weak interaction such as hydrogen bonding, Vanderwaals force etc., between the amino acids present in the active site and the substrate.
When a drug molecule that has a similar geometry (shape)as the substrate is administered, it can also bind to the enzyme and inhibit its activity. In other words, the drug acts as an inhibitor to the enzyme catalyst. These types of inhibitors are often called competitive inhibitors.
In certain enzymes, the inhibitor molecule binds to a different binding site, which is commonly referred to as an allosteric site and causes a change in its active site geometry (shape). As a result, the substrate cannot bind to the enzyme. These types of inhibitors are called allosteric inhibitors.
