in bacteria, antibacterial sulfonamides act as competitive inhibitors of the enzyme dihydropteroate synthase, 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.