Answer to Question #259560 in General Chemistry for Pogi

Question

 Explain the difference in the mechanism of action of penicillin and sulfanilamide. How is enzyme inhibition involved in bot mechanisms? Why don’t penicillin and sulfanilamide kill both human and bacterial cells?

Answer 1

As a sulfonamide antibiotic, sulfanilamide functions by competitively inhibiting (that is, by acting as a substrate analogue) enzymatic reactions involving para-aminobenzoic acid (PABA). Specifically, it competitively inhibits the enzyme dihydropteroate synthase.

Penicillin and one of the sulfonamide compounds are frequently used simultaneously in treatment of serious infections in an attempt to enhance the therapeutic effect. Ungar,1 in 1943, reported that sulfapyridine potentiated the action of penicillin, both in vitro and in a limited number of infected mice. Soo-Hoo and Schnitzer2 confirmed Ungar's claim that penicillin and various sulfonamide drugs were synergistic in combatting streptococcic infections in mice. They also showed that penicillin could prevent the inhibiting action of paraaminobenzoic acid on the sulfonamide drugs.