Higher affinity of a binding site corresponds to a lower value of which constant?

Higher affinity of a binding site corresponds to a lower value of which constant?

• A. Kd
• B. Km
• C. Ki
• D. Vmax

Answer: (A)

The correct answer is the dissociation constant, often represented as Kd. The dissociation constant (Kd) is a measure of the affinity between a ligand and a protein, such as an enzyme or a receptor. A lower Kd value indicates that the ligand binds more tightly to the binding site, which corresponds to a higher affinity. This means that less of the ligand is required to occupy half of the available binding sites, thus reflecting strong interactions. In contrast, Km (Michaelis constant) is associated with enzyme kinetics and indicates the substrate concentration at which the reaction rate is half of Vmax. A lower Km indicates higher affinity between the enzyme and the substrate, but it is not directly related to the context of binding affinity in the same way Kd is. Ki refers to the inhibition constant, which measures the effectiveness of an inhibitor and is related to the binding of an inhibitor to an enzyme. While a lower Ki signifies a stronger inhibitor, it is also not the most appropriate measure of binding affinity between a ligand and a receptor. Vmax is the maximum rate of an enzymatic reaction when the enzyme is saturated with substrate. It does not reflect binding affinity but rather the capacity of the enzyme to catalyze a reaction. Thus, a higher

The correct answer is the dissociation constant, often represented as Kd. The dissociation constant (Kd) is a measure of the affinity between a ligand and a protein, such as an enzyme or a receptor. A lower Kd value indicates that the ligand binds more tightly to the binding site, which corresponds to a higher affinity. This means that less of the ligand is required to occupy half of the available binding sites, thus reflecting strong interactions.

In contrast, Km (Michaelis constant) is associated with enzyme kinetics and indicates the substrate concentration at which the reaction rate is half of Vmax. A lower Km indicates higher affinity between the enzyme and the substrate, but it is not directly related to the context of binding affinity in the same way Kd is.

Ki refers to the inhibition constant, which measures the effectiveness of an inhibitor and is related to the binding of an inhibitor to an enzyme. While a lower Ki signifies a stronger inhibitor, it is also not the most appropriate measure of binding affinity between a ligand and a receptor.

Vmax is the maximum rate of an enzymatic reaction when the enzyme is saturated with substrate. It does not reflect binding affinity but rather the capacity of the enzyme to catalyze a reaction.

Thus, a higher