The relationship between sulphonamide and PABA is
Sulfonamides have structural similarity with PABA .therefore, they competitively inhibit the enzyme responsible for the incorporation of PABA into dihydropteroic acid, the immediate precursor of folic acidRef: DM Vasudevan, 7th edition, page no: 491, 61
Metabolic antagonism
Synergism
Intermediate compound formation
Chelation
Metabolism of nucleic acids