Inhibit synthesis of purine and thymidylate precursor’s folic acid or tetrahydrofolate.
Sulfonamides:
- Competitively inhibits dihydropteroate synthase, an enzyme that converts p-aminobenzoic acid (PABA) into folic acid. These drugs can also be incorporated into a compound that resembles dihydrofolate and that in turn can inhibit another enzyme in the pathway, dihydrofate reductase. Sulfonomides inhibit bacteria-specific reaction. Inhibits dihydrofolate reductase, blocking tetrahydrofolate synthesis.
Dapsone: - Interferes with synthesis of folic acid, which is required for the synthesis of purines and thymidine and for the synthesis of the amino acids methionine and gycine.
Trimethoprim:
- Inhibits dihydrofolate reductase, blocking tetrahydrofolate synthesis.