Aminoglycoside-modifying enzymes (AMEs) are the most common mechanism of aminoglycoside resistance. The enzyme class that reduces the positive charge on aminoglycosides, impairing their electrostatic uptake into bacteria, is:

• A Nucleotidyltransferases (ANT) adding nucleotide groups to hydroxyl groups
• B Phosphotransferases (APH) adding phosphate groups to hydroxyl groups
• C 16S rRNA methyltransferases directly modifying the ribosomal binding site
• D Acetyltransferases (AAC) adding acetyl groups to amino groups ✓

Explanation

Acetyltransferases (AAC enzymes) acetylate the amino groups of aminoglycosides. Since aminoglycosides rely on positive charge (from protonated amino groups) for electrostatic binding to the negatively charged outer membrane and subsequent energy-dependent uptake, acetylation neutralises these charges and drastically reduces uptake into bacterial cells. APH and ANT enzymes modify hydroxyl groups but primarily affect ribosomal binding. 16S methyltransferases (e.g., ArmA) confer pan-aminoglycoside resistance by methylating the drug binding site on the 30S ribosome.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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