Sulfonamides and trimethoprim animation: folic acid inhibitors 

sulfonamide and trimethoprim inhibit bacterial folic acid diffrent stages. Dihydropteroate enzyme catalyze the synthesis of bacterial folic acid. Sulfonamide antibiotics inhibit dihydropteroate enzyme thus interfere with folic acid synthesis. Dihydrofolate reductase catalyze the conversion of tetrahydrofolic acid in human and bacteria. Trimethoprim inhibits this enzyme.