GATE 2022 BT – Question 19
Which of the following statements about reversible enzyme inhibitors are CORRECT? P. Uncompetitive inhibitors bind only to the enzyme-substrate complex Q. Non-competitive inhibitors bind only at a different site from the substrate R. Competitive inhibitors bind to the same site as the substrate
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Correct answer: (D) P, Q and R
Explanation
Classify the three types of reversible inhibitors by where they bind.
- **P. Uncompetitive inhibitors bind only to the enzyme-substrate (ES) complex.** True. They lower both $V_{max}$ and $K_m$ by the same factor. ✓
- **Q. Non-competitive inhibitors bind only at a site different from the substrate site.** True. In the classical model they bind E and ES equally well at an allosteric site and lower $V_{max}$ without changing $K_m$. ✓
- **R. Competitive inhibitors bind to the same site as the substrate.** True. They compete with the substrate for the active site and raise the apparent $K_m$ without changing $V_{max}$. ✓
All three statements are correct: **P, Q and R** (D).