Trimethoprim acts by:
Trimethoprim, Methotrexate and pyrimethamine inhibits dihydrofolate reductase enzyme and prevents formation of Tetrahydrofolic acid and from Dihydrofolic acid.
Inhibiting peptidyl transferase enzyme
Inhibiting dihydrofolate reductase enzyme
Inhibiting Dihydropteroate synthase enzyme
Binds to 50s ribosomal unit and prevents protein synthesis