Folic acid synthesis in bacteria
Sulfanilamide is known to be sulfonamide antibiotic with a wide spectrum against most gram -ve and gram +ve organisms. Thus, sulfonamide is a competitive inhibitor of dihydropteroate synthetase a bacterial enzyme that uses parabenzoic acid (PABA) for the synthesis folic acid. However, inhibition of this enzyme by sulfonamide will prevent the synthesis of folic acid which is very important for bacterial replication. Similarly, sulfonamides inhibit the multiplication of bacteria by acting as competitive inhibitor of PABA.