Question

Two statements in respect of drug-enzyme interaction are given below 

Statement I: Action of an enzyme can be blocked only when an inhibitor blocks the active site of the enzyme. 

Statement II: An inhibitor can form a strong covalent bond with the enzyme. 

In the light of the above statements, choose the correct answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Answer 1

The Correct Option is D

To determine the correct answer, we need to evaluate each statement based on the concept of enzyme inhibition:

• Statement I: Action of an enzyme can be blocked only when an inhibitor blocks the active site of the enzyme.
  • This statement is false. Inhibition of enzyme activity can occur through multiple mechanisms:
  • Competitive Inhibition: Inhibitors that resemble the substrate physically block the active site.
  • Allosteric (Non-competitive) Inhibition: Inhibitors bind to sites other than the active site, causing a change in enzyme shape and reducing its activity.
  • Uncompetitive Inhibition: Inhibitors bind to the enzyme-substrate complex, affecting enzyme action.
• Statement II: An inhibitor can form a strong covalent bond with the enzyme.
  • This statement is true. When an inhibitor forms a covalent bond with an enzyme, it results in irreversible inhibition.
  • Such covalent attachment prevents the enzyme from returning to its active form.
  • Examples include enzyme inhibitors like aspirin, which acetylates and irreversibly inhibits cyclooxygenase.

Based on the analysis above, the correct answer is: Statement I is false but Statement II is true.