Final answer:
To evaluate Kcat, the enzyme needs to be saturated with substrate. Specifically, all active sites on the enzyme molecules must be bound to substrate molecules to measure the enzyme's maximum catalytic activity. Conditions like being denatured, catalytically inactive, or inhibitor-bound would impede this measurement.
Step-by-step explanation:
To evaluate Kcat, which is a measure of the catalytic activity of an enzyme, it's necessary for the enzyme to be in a state where it is saturated with substrate. This means that the active sites on all enzyme molecules are bound with substrate molecules, ensuring that the catalytic activity measured is at its maximum and not limited by the availability of the substrate. This state can be contrasted with an enzyme being denatured, catalytically inactive, or inhibitor-bound, which are conditions that would prevent an accurate measurement of Kcat.
The effect of an inhibitor binding to an enzyme is typically to inactivate the enzyme, preventing it from catalyzing its reaction. Specifically, a competitive inhibitor will bind to the same active site as the substrate, blocking the substrate from binding and thus preventing the enzyme from performing its catalytic function. This concept is fundamental to understanding enzyme kinetics, including enzyme inhibition which can be reversible or irreversible, impacting the measurement of enzyme activity.