Vancomycin kills gram-positive bacteria by binding to which specific substrate?

• A Lipid II (undecaprenyl-pyrophosphate-MurNAc-pentapeptide)
• B Transglycosylase active site
• C Lipopolysaccharide of the outer membrane
• D D-Ala-D-Ala terminus of the pentapeptide side chain ✓

Explanation

Vancomycin is a glycopeptide antibiotic that forms hydrogen bonds with the D-Ala-D-Ala terminus of the peptide side chain on peptidoglycan precursors, sterically blocking both transglycosylation and transpeptidation. VRE resistance arises from replacing D-Ala-D-Ala with D-Ala-D-Lac, reducing binding affinity 1000-fold. It targets cell wall synthesis but acts on the substrate, not the enzyme active site directly.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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