In which type of inhibition does the inhibitor only bind to the enzyme-substrate complex?

The correct answer is uncompetitive inhibition. In uncompetitive inhibition, the inhibitor specifically binds to the enzyme-substrate complex, which prevents the complex from releasing the products. This action effectively decreases both the rate of reaction and the maximum velocity (Vmax) of the reaction because it reduces the amount of enzyme-substrate complex available for conversion into product. The binding of the inhibitor to the enzyme-substrate complex results in a more stable complex that cannot proceed to the product formation, which is a defining characteristic of uncompetitive inhibition.

This type of inhibition is distinctive because it does not compete with the substrate for the active site; rather, it binds only when the substrate is already present. This contrasts with competitive inhibition, where the inhibitor directly competes with the substrate for binding to the active site of the enzyme. Non-competitive inhibition involves an inhibitor that can bind to either the enzyme or the enzyme-substrate complex, reducing the overall number of active enzyme molecules regardless of substrate presence. Feedback inhibition refers to a regulatory mechanism in metabolic pathways but does not fit the binding dynamics described in the question.