This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzyme basics and serine proteases, Subject name: Biochemistry
All of the following are examples for mechanism based inhibition, EXCEPT: 
Select and explain. 
A. Aspirin on cyclooxygenase, B. Allopurinol on Xanthine oxidase, C. Statins on HMG-CoA reductase, D. Difluoromethylornithine on ornithine decarboxylase
C: Statins on HMG-CoA reductase
Answer: C: Statins on HMG-CoA reductase 
Explanation: Mechanism-based inhibition/Suicidal inhibition: Suicidal inhibitors resemble the actual substrate of the enzyme. Enzymes binds to suicidal inhibitor & catalytic process is staed. In the process of catalysis, enzyme undergoes irreversible covalent modification by the inhibitor & active enzyme can't be regenerated. (Enzyme catalyses its own destruction) Suicidal Inhibitor Enzyme Allopurinol Xanthine oxidase Aspirin Cyclooxygenase 5-FU Thymidylate synthase Penicillin Transpeptidase Difluoromethylornithine Ornithine decarboxylase