The active site of an enzyme is where the substrate binds and the chemical reaction takes place. It is a specific region of the enzyme that is complementary in shape and charge to the substrate, allowing for precise and efficient catalysis of the reaction.
On the other hand, the allosteric site is a separate binding site on the enzyme that can regulate the activity of the enzyme. When a molecule binds to the allosteric site, it can either activate or inhibit the enzyme, changing its shape and affecting its ability to bind to the substrate at the active site.
In summary, the active site is where the substrate binds and the reaction occurs, while the allosteric site is a regulatory site that can modulate the activity of the enzyme.