Alexander Fleming – discoverer of Penicillin antibiotics

Alexander Fleming – discoverer of Penicillin antibiotics

Alexander Fleming – discoverer of Penicillin antibiotics

Biography & Contributions

Alexander Fleming was a Scottish biologist, pharmacologist, botanist and Nobel laureate born on August 06, 1881 – died on March 11, 1955. Fleming best-known discoveries are the enzyme lysozyme and the antibiotic substance benzylpenicillin (Penicillin G) from the mould Penicillium notatum.

Lysozyme occurs in white blood cells, egg whites, milk, pus, saliva, and tears, and engulfs and digests bacteria, forming a key component in the body's defense system.

In November 1921 Fleming discovered lysozyme, an enzyme present in body fluids such as saliva and tears that has a mild antiseptic effect. That was the first of his major discoveries.

Fleming noticed that a culture plate of Staphylococcus aureus he had been working on had become contaminated by a fungus. A mold, later identified as Penicillium notatum had inhibited the growth of the bacteria. He at first called the substance mould juice and then penicillin.

He investigated its positive anti-bacterial effect on many organisms, and noticed that it affected bacteria such as staphylococci and many other Gram-positive pathogens that cause scarlet fever, pneumonia, meningitis and diphtheria, but not typhoid fever or paratyphoid fever.

Fleming's accidental discovery and isolation of penicillin in September 1928 marks the start of modern antibiotics.Fleming was the first to push these studies further by isolating the penicillin, and by being motivated enough to promote his discovery at a larger scale.Fleming also discovered very early that bacteria developed antibiotic resistance whenever too little penicillin was used or when it was used for too short a period.

Penicillin Antibiotic

Penicillin antibiotics were among the first drugs to be effective against many previously serious diseases, such as bacterial infections caused by staphylococci and streptococci. Penicillins are still widely used today, though misuse has now made many types of bacteria resistant.

It is a group of antibiotics derived from Penicillium fungi, including penicillin G (intravenous use), penicillin V (oral use), procaine penicillin, and benzathine penicillin (intramuscular use).

Penicillin Biosynthesis

1] The first step is the condensation of three amino acids - L-α-aminoadipic acid, L-cysteine, L-valine into a tripeptide.

2] The second step in the biosynthesis of penicillin G is the oxidative conversion of linear ACV into the bicyclic intermediate isopenicillin N by isopenicillin N synthase (IPNS).

3] The final step is a transamidation by isopenicillin N N-acyltransferase, in which the α-aminoadipyl side-chain of isopenicillin N is removed and exchanged for a phenylacetyl side-chain.

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