Penicillin -- An Interesting Organic Molecule

Penicillin is one of the most influential antibiotics of the 20th century. Its antibiotic activity results from its ability to acylate (put an acyl group on) a CH2OH group of an enzyme that helps build bacterial cell walls. This acylation deactivates the enzyme, causing growing bacteria to die as they are unable to synthesize functional cell walls. Penicillin has no effect on normal body cells because they do not have cell walls.

Discovery & History

The antibiotic was first discovered by Alexander Fleming in 1928 at the University of London. The story goes that Fleming was about to throw out a culture of staphylococcal bacteria that was contaminated with a rare mold Penicillium notatum when he noticed that wherever the mold was, the bacteria disappeared. He correctly hypothesized that the mold contained an antibacterial substance. It wasn't until a decade later that Howard Florey and Ernest Chain isolated the compound, penicillin-G. The three scientists shared the Nobel Prize for their work in 1945. Penicillin was first produced for the military and war casualties. The drug became available for civilian use in 1944.

Clinical Use

More than ten different types of penicillin are currently in clinical use. These only differ structurally in that the group (R) that is attached to the carbonyl group varies. These various penicillins also differ in the organisms against which they are most effective. Penicillin is used often today to treat staphylococci and streptococci. Misuse/overuse of penicillin has made many types of bacteria resistant to its effects.

Drug Resistance

In 1940, Ernest Chain discovered an enzyme that destroys penicillin, penicillinase. Some bacteria are resistant to penicillin because they secrete this enzyme. Penicillinase causes the product to have no antibacterial activity.The different types of penicillin differ in their susceptibility to penicillinase. 

Fun Fact

Almost 19% of humans are allergic to penicillin-G.

References

Bruice, Paula Yurkanis. Organic Chemistry. Upper Saddle River, NJ: Prentice Hall, 2014. Print.