L-Tyrosine is a nonessential amino acid, meaning that it is manufactured in the human body and does not need to be supplied in the diet. Under certain physiological conditions, however, it may need to be supplemented.
Like most natural amino acids, the α carbon atom in tyrosine has the L-configuration; but its enantiomer, D-tyrosine, also occurs in nature. In 1846, German chemist J. von Liebig discovered L-tyrosine in casein obtained from cheese. E. Abderhalden and Y. Teruuchi, also in Germany, isolated it from silk waste in 1906.
The body uses L-tyrosine to build proteins, many of which are involved in signal transduction. In plants, the amino acid is an electron donor in the process of photosynthesis.
Recently, V. J. J. Martin and co-workers at Concordia University (Montreal) engineered an enzyme to convert L-tyrosine to L-DOPA. This was part of a larger project to produce opiates such as codeine and morphine from yeasts, which make L-tyrosine from glucose. To aid in the enzyme screening, the research team developed a biosensor that turns L-DOPA yellow so that it biosynthesis can be tracked easily.
MOTW Update: April 25, 2016
L-Tyrosine is in the news again. Scientists at Cornell University and the University of Wisconsin–Madison showed that medically useful isoquinolines, formerly thought to be biosynthesized only by plants, can be made by a fungus. Aspergillus fumigatus uses the amino acid as the starting material to synthesize a variety of the heterocyclic molecules. The fungus and plant mechanisms are similar but evolutionarily independent.
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