L-Tyrosine

Absorption

L-tyrosine is absorbed from the small intestine by a sodium-dependent active transport process.

Toxicity

L-Tyrosine has very low toxicity. There have been very few reports of toxicity. LD50 (oral, rat) > 5110 mg/kg.

Description

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.

The Uses of L-Tyrosine

L-Tyrosine, one of the 22 proteinogenic amino acids essential for protein synthesis, serves as a crucial precursor for several important neurotransmitters. Derived from L-phenylalanine, it undergoes biological conversion to L-DOPA, subsequently leading to the synthesis of dopamine, norepinephrine, and epinephrine.

Background

Tyrosine is a non-essential amino acid. In animals it is synthesized from phenylalanine. It is also the precursor of epinephrine, thyroid hormones, and melanin.

Indications

Tyrosine is claimed to act as an effective antidepressant, however results are mixed. Tyrosine has also been claimed to reduce stress and combat narcolepsy and chronic fatigue, however these claims have been refuted by some studies.

Metabolism

In the liver, L-tyrosine is involved in a number of biochemical reactions, including protein synthesis and oxidative catabolic reactions. L-tyrosine that is not metabolized in the liver is distributed via the systemic circulation to the various tissues of the body.