Today in my Microbiology lab we set up an experiment to test the hypothesis that sulfa drugs work by competitive inhibition of an enzyme crucial for synthesis of folic acid, which is a precursor for amino acids and nucleic acids, in bacteria.
Sulfa drugs were discovered by Gerhard Dormagk, a German pathologist and bacteriologist around the time of World War II. At this time, people were dying not from the wounds they sustained during the war, but from the bacterial infection that festered in these wounds. These were the times before penicillin.
Dormagk ran structured tests to see what drug would work against these bacteria and he finally discovered these sulfa drugs- more commonly- sulfonamide or sulfanilimide.
These drugs work by competitive inhibition at the active site of the DHPS enzyme that catalyzes the formation of p-amino benzoic acid (PABA) to folic acid, which is a precursor for biosynthesis of amino acids and nucleic acids. Essentially, the drug prevents the bacteria from making folic acid and so the bacteria cannot thrive. Fortunately, humans do not make folic acid (we have to ingest it) so this drug does not affect us.
Before the drug was available on the market, Dormagk's daughter became ill with strep. She was not responding to the treatment available at that time, so he decided to give this drug to her. She recovered, and this was instant proof for the viability of these drugs for widespread use.
During the war, soldiers would have pouches filled with some of this drug in powdered form. The use of sulfanilimide greatly reduced the fatalities due to bacterial infection of wounds during this time.
Eventually, when penicillin and other antibiotics were discovered, sulfa drugs began to lose favor. However, today with the prevalence of HIV/AIDS and antibiotic resistance, these drugs are beginning to make a comeback.