In which type of inhibition is Vmax unchanged?

In the context of enzyme kinetics, competitive inhibition is characterized by a scenario where the inhibitor competes with the substrate for binding to the active site of the enzyme. Because the inhibitor directly competes with the substrate, increasing the concentration of the substrate can outcompete the inhibitor. As a result, in the presence of sufficient substrate, the reaction can still reach its maximum velocity (Vmax), which remains unchanged.

While the apparent affinity for the substrate decreases, reflected in an increase in the Michaelis constant (Km), the Vmax remains constant because it is dependent on the total amount of enzyme available, which is unchanged by the competitive inhibitor. Therefore, if enough substrate is present, the enzyme can still achieve its full catalytic capacity, leading to the same Vmax as without the inhibitor.

In contrast, non-competitive inhibition affects Vmax because the inhibitor can bind to the enzyme regardless of whether the substrate is present, effectively reducing the number of active enzyme sites and thus the maximum possible rate of reaction. Uncompetitive inhibition leads to a decrease in both Km and Vmax, as the inhibitor binds only to the enzyme-substrate complex. Mixed inhibition can affect both Vmax and Km, depending on the specifics of how the inhibitor interacts with the enzyme-substrate