Which class inhibits folic acid synthesis in bacteria by targeting dihydropteroate synthase?

Which class inhibits folic acid synthesis in bacteria by targeting dihydropteroate synthase?

• A. Aminoglycosides
• B. Penicillins
• C. Macrolides
• D. Sulfonamides

Answer: (D)

Folate synthesis in bacteria relies on dihydropteroate synthase to convert PABA into the next folate precursor. Sulfonamides mimic PABA and competitively inhibit this enzyme, effectively blocking folate production needed for DNA synthesis and bacterial growth. Humans don’t synthesize folate de novo and obtain it from the diet, so they’re less affected, giving selective toxicity to bacteria. The other drug classes target different processes: aminoglycosides disrupt protein synthesis at the 30S ribosomal subunit, penicillins inhibit cell wall synthesis, and macrolides block protein synthesis at the 50S subunit.

Folate synthesis in bacteria relies on dihydropteroate synthase to convert PABA into the next folate precursor. Sulfonamides mimic PABA and competitively inhibit this enzyme, effectively blocking folate production needed for DNA synthesis and bacterial growth. Humans don’t synthesize folate de novo and obtain it from the diet, so they’re less affected, giving selective toxicity to bacteria. The other drug classes target different processes: aminoglycosides disrupt protein synthesis at the 30S ribosomal subunit, penicillins inhibit cell wall synthesis, and macrolides block protein synthesis at the 50S subunit.