Which statement is true regarding non-competitive inhibitors?

Non-competitive inhibitors are a specific type of enzyme inhibitors that bind to an allosteric site, which is distinct from the active site of the enzyme. This binding alters the enzyme's conformation, affecting its ability to catalyze reactions, regardless of whether the substrate is present or not. Even when the substrate binds to the active site, the enzyme's activity is reduced because the inhibitor changes the way the enzyme functions without blocking the active site directly. This is crucial for understanding enzyme kinetics and the regulatory mechanisms of metabolic pathways.

In contrast to non-competitive inhibitors, other options describe interactions that do not accurately represent the behavior of non-competitive inhibition. For instance, binding to the active site corresponds to competitive inhibition, which is different. Changing the enzyme’s primary structure refers to processes such as mutations or post-translational modifications, not to reversible inhibition by non-competitive inhibitors. Lastly, non-competitive inhibitors do not increase the reaction rate; instead, they decrease it, as they reduce the overall efficacy of the enzyme regardless of substrate concentration. Therefore, recognizing that non-competitive inhibitors interact with the allosteric site provides a clearer understanding of their mechanism and impact on enzyme activity.