DEFINITION
Tyrosine is a nonessential amino acid with the chemical formula C9H11NO3. It is produced in the body from phenylalanine and is a precursor of melanin and of several neurotransmitters and hormones, such as epinephrine and thyroxine[1].
DISCOVERY
The German chemist Justus Freiherr von Liebig discovered[2] tyrosine in 1846 while experimenting with cheese. In his 1846 publication the extraction process was described as below:
- Crude casein was mixed with equal amounts of potassium hydroxide.
- Hot water and acetic acid were then added to the resultant mass.
- Upon cooling, needle-like crystals were formed.
Here is a photomicrograph[3] of tyrosine crystals:
DISCOVERER
Here is a portrait [4] of Justus Freiherr von Liebig:
1803-1873