Competitive inhibition is a form of enzyme inhibition where binding of the inhibitor to the enzyme prevents binding of the substrate and vice versa. This can occur in two ways:

In classical competitive inhibition, the inhibitor binds to the same active site as the normal enzyme substrate, without undergoing a reaction. The substrate molecule cannot enter the active site while the inhibitor is there, and the inhibitor cannot enter the site when the substrate is there.In this case, the maximum speed of the reaction is unchanged, because although the substrate's apparent affinity for the site is decreased, the substrate concentration will eventually increase to match the concentration of the inhibitor.

In Non-classical or allosteric competitive inhibition, the inhibitor binds away from the active site, creating a conformational change in the enzyme such that the substrate can no longer bind to it. Consequently, adding more substrate will not increase the reaction rate. Thus, the reaction rate cannot reach its maximum velocity.

Enzyme kinetics

Inhibidor competitivo