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MBBS QUESTION #10320
Question 1
A non-competitive enzyme inhibitor, which binds a site distinct from the active site (on either free enzyme or the enzyme-substrate complex), characteristically produces which kinetic effect?
  • Decreased $V_{max}$, while $K_m$ remains unchanged, since the inhibition cannot be overcome by increasing substrate concentration✔️
  • Increased $K_m$ with unchanged $V_{max}$
  • Increased both $K_m$ and $V_{max}$
  • Binding is restricted exclusively to free enzyme, never the enzyme-substrate complex
Correct Answer Explanation
A non-competitive inhibitor reduces the effective concentration of functional enzyme regardless of substrate concentration, lowering the achievable $V_{max}$; because it does not compete with substrate for the active site, the enzyme's intrinsic affinity for substrate ($K_m$) is unaffected.