In mixed inhibition, what characterizes the inhibitor?

In mixed inhibition, the distinctive characteristic of the inhibitor is its ability to bind to both the free enzyme and the enzyme-substrate complex. This dual binding capacity affects the activity of the enzyme in a complex manner.

When the inhibitor binds to the free enzyme, it can prevent the substrate from binding by altering the enzyme's active site. Conversely, if the inhibitor binds to the enzyme-substrate complex, it can prevent the complex from releasing the product, thereby inhibiting the progress of the reaction. This mode of action leads to changes in both the maximum velocity (Vmax) and the Michaelis constant (Km) of the enzyme's activity, as the apparent affinity for the substrate can vary based on the concentration of the inhibitor.

By understanding that mixed inhibitors influence the reaction dynamics through interactions with both forms of the enzyme, we can appreciate their complexity compared to other forms of inhibition, such as competitive or non-competitive inhibition. This foundational knowledge is crucial for interpreting enzyme kinetics and the effects of various inhibitors.