Dihydropteroate synthase inhibitor
In bacteria, antibacterial sulfonamides act as competitive inhibitors of the enzyme dihydropteroate synthetase, DHPS. DHPS catalyses the conversion of PABA (para-aminobenzoate) to dihydropteroate, a key step in folate synthesis. Folate is necessary for the cell to synthesize nucleic acids (nucleic acids are essential building blocks of DNA and RNA), and in its absence cells will be unable to divide. Hence the sulfonamide antibacterials exhibit a bacteriostatic rather than bactericidal effect.
Folate is not synthesized in mammalian cells, but is instead a dietary requirement. This explains the selective toxicity to bacterial cells of these drugs. These antibiotics are used to treat pneumocystis jiroveci pneumonia, urinary tract infections, and shigellosis.
Pharmacology: enzyme inhibition Class SubstrateOxidoreductase (EC 1)Transferase (EC 2)Hydrolase (EC 3)Lyase (EC 4)
4.1 Dopa decarboxylase4.2 Carbonic anhydrase
Antibacterials: nucleic acid inhibitors (J01E, J01M) Antifolates
DNA and RNA synthesis)Sulfonamides
DNA replication)1st g.2nd g.3rd g.4th g.Vet.Related (DG)
RNA synthesis #WHO-EM. ‡Withdrawn from market. Clinical trials: †Phase III. §Never to phase III Antiparasitics – antiprotozoal agents – Chromalveolate antiparasitics (P01) Alveo-
(antifols)Sulfadoxine • sulfamethoxypyrazineCoformulationFansidar# (sulfadoxine/pyrimethamine)OtherCombi-
nationsFixed-dose (coformulated) ACTsOther combinations
(not co-formulated)artesunate/SP • artesunate/mefloquine •
quinine/tetracycline • quinine/doxycycline • quinine/clindamycin
#WHO-EM. ‡Withdrawn from market. Clinical trials: †Phase III. §Never to phase III Antimycobacterials, including tuberculosis treatment and leprostatic agents (J04) Nucleic acid inhibitorAntifolates/DSIASA4-Aminosalicylic acid# (Calcium aminosalicylate, Sodium aminosalicylate) Protein synthesis inhibitor Cell envelope antibioticPeptidoglycan layerArabinogalactan layerMycolic acid layer Other/unknown CombinationsRifampicin/isoniazid/pyrazinamide #WHO-EM. ‡Withdrawn from market. Clinical trials: †Phase III. §Never to phase III This antiinfective drug article is a stub. You can help Wikipedia by expanding it.