In the presence of an uncompetitive inhibitor that binds __________ the substrate, the apparent V_max ____________ and the apparent K_m ____________ with respect to the V_max and K_m of the uninhibited enzyme.

• A. Before, Decreases, Increases.
• B. After, Decreases, Decreases.
• C. After, Increases, Increases.
• D. Before, Stays the same, Decreases.
• E. After, Decreases, Stays the same.

Answer: (B)

Verified step by step guidance

1. Understand the concept of enzyme inhibition: Uncompetitive inhibitors bind to the enzyme-substrate complex, not the free enzyme. This affects both the Vmax and Km values.
2. Identify the effect of uncompetitive inhibition on Vmax: Uncompetitive inhibitors decrease the apparent Vmax because they prevent the enzyme from converting substrate to product efficiently.
3. Identify the effect of uncompetitive inhibition on Km: Uncompetitive inhibitors also decrease the apparent Km because they stabilize the enzyme-substrate complex, making it seem like the enzyme has a higher affinity for the substrate.
4. Consider the timing of inhibitor binding: Uncompetitive inhibitors bind after the substrate has bound to the enzyme, forming the enzyme-substrate complex.
5. Match the correct answer with the effects: The correct answer should reflect that uncompetitive inhibitors bind after the substrate, decrease the apparent Vmax, and decrease the apparent Km.