An enzyme has a Vmax of 100 µmol/min without an inhibitor. In the presence of a noncompetitive inhibitor, the Vmax decreases to 50 µmol/min. What is the effect on the reaction rate at high substrate concentrations?

• A. The reaction rate is unaffected by the inhibitor at high substrate concentrations.
• B. The reaction rate increases at high substrate concentrations.
• C. The reaction rate remains the same at high substrate concentrations.
• D. The reaction rate decreases to half of its original value at high substrate concentrations.

Answer: (D)