An enzyme is more effectively inhibited by uncompetitive inhibitors when both substrate and inhibitor concentrations are:

Uncompetitive inhibition occurs when an inhibitor binds to the enzyme-substrate complex, preventing the complex from being converted into a product. This type of inhibition is unique in that the presence of the substrate increases the effectiveness of the inhibitor; the inhibitor binds only to the enzyme after the substrate has successfully bound.

When both substrate and inhibitor concentrations are increased and made equal, the likelihood of the inhibitor binding to the enzyme-substrate complex also increases, resulting in a more significant reduction in enzyme activity. The uncompetitive inhibitor effectively limits the maximum reaction rate (Vmax) while also reducing the apparent Michaelis constant (Km) because the inhibitor stabilizes the enzyme-substrate complex.

Thus, having both concentrations high and equal enhances the interaction between them, leading to profound inhibition. The synergy of having equal high levels of substrate and inhibitor maximizes the impact of the uncompetitive inhibitor, which is why this particular scenario is optimal for such inhibitors. This makes the choice reflecting increased and equal concentrations the best response for understanding the kinetics of uncompetitive inhibition.