A microbiologist notes that a bacterial isolate produces an enzyme that opens the beta-lactam ring of penicillin. This beta-lactamase is inhibited by clavulanic acid. The mechanism by which clavulanic acid inhibits beta-lactamase is best described as:

• A Competitive reversible inhibition at the active site
• B Irreversible suicide inhibition forming a covalent acyl-enzyme complex ✓
• C Allosteric inhibition at a site distant from the active serine
• D Chelation of zinc from metallo-beta-lactamase active site

Explanation

Clavulanic acid is a progressive irreversible (suicide) inhibitor of serine beta-lactamases. It binds to the active site serine of the enzyme, forming an acyl-enzyme complex that undergoes further rearrangements to permanently inactivate the enzyme. Because clavulanic acid itself is hydrolyzed in this process (sacrificing itself), it is called a suicide inhibitor. It does not inhibit metallo-beta-lactamases, which use zinc and are inhibited by metal chelators like EDTA.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.