Fosfomycin tromethamine is given as a single oral dose for uncomplicated cystitis. Its antibacterial action results from irreversible inhibition of which enzyme?
- A Transpeptidase involved in cross-linking of peptidoglycan
- B MurA, UDP-N-acetylglucosamine enolpyruvyl transferase ✓
- C Undecaprenyl pyrophosphate synthase
- D Alanine racemase
Correct answer: B. MurA, UDP-N-acetylglucosamine enolpyruvyl transferase
Explanation
Fosfomycin is a phosphonic acid analogue that irreversibly inhibits MurA, the enolpyruvyl transferase catalyzing the first committed cytoplasmic step of peptidoglycan synthesis, namely condensation of UDP-N-acetylglucosamine with phosphoenolpyruvate. This step precedes transpeptidation, which beta-lactams target at the membrane level. Alanine racemase is inhibited by cycloserine, and undecaprenyl pyrophosphate cycling is disrupted by bacitracin.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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