Which factor is primarily affected by non-competitive inhibition?

Non-competitive inhibition primarily affects Vmax, which represents the maximum rate of an enzymatic reaction when the enzyme is saturated with substrate. In non-competitive inhibition, an inhibitor can bind to an enzyme whether or not the substrate is present, resulting in a decrease in the overall number of active enzyme molecules available to catalyze the reaction. This leads to a lower Vmax because, even when the substrate concentration is increased, the presence of the inhibitor prevents the enzyme from achieving its maximum reaction rate.

On the other hand, the Km value, which indicates the affinity between the enzyme and the substrate, remains unchanged in non-competitive inhibition. This is because the inhibitor does not prevent the substrate from binding to the enzyme; instead, it alters the catalytic activity of the enzyme. The affinity is not altered because the enzyme can still interact with the substrate, but the efficiency of the conversion of the substrate to the product is reduced. Reaction time is not a standard consideration in the context of enzyme kinetics in the same way as Vmax and Km are.