L-Tyrosine(LT) is given as a supplement to increase L-Tyrosine levels in people with PKU.L-tyrosine is an important amino acid that is widely applied in the food, feed, medicines, chemical and cosmetics industries[1,2]. Due to its ability to enhance memory and mental acuity, it is widely used as a dietary supplement and appetite suppressant.

L-Tyrosine has been used in alternative medicine as a possibly effective aid in improving mental performance, alertness, or memory. L-Tyrosine is a proteinogenic amino acid that crystallizes in an orthorhombic noncentrosymmetric structure (P212121)[3]. 

L-Tyrosine has also been used to treat depression or attention deficit disorder (ADD or ADHD). However, research has shown that L-Tyrosine may not be effective in treating these conditions. L-Tyrosine also may not be be effective in improving exercise performance. Other uses not proven with research have included dementia, high blood pressure, narcolepsy, schizophrenia, weight loss, premenstrual syndrome, Parkinson's disease, chronic fatigue syndrome, alcoholism, cocaine addiction, and other conditions.

Fig 1. Chemical structure formula of L-Tyrosine

L-tyrosine is used as a crucial precursor of various high-value compounds in primary medications, such as L-DOPA for the treatment of Parkinson’s disease and p-hydroxycinnamic acid for nutrition products[4].

L-tyrosine, an aromatic polar α-amino acid containing a phenolic hydroxyl group, is an essential amino acid and ketogenic/glycogenic amino acids found in human and other mammalian bodies. L-tyrosine is a significant precursor of several neurotransmitters, catecholamine and hormones, such as dopamine, norepinephrine, epinephrine, thyroxin, as well as other physiologically important biological small molecules. L-tyrosine also involved in the construction of almost every protein in the body[5,6].

L-Tyrosine is not certain whether L-Tyrosine is effective in treating any medical condition. Medicinal use of this product has not been approved by the FDA. L-Tyrosine should not be used in place of medication prescribed for you by your doctor. L-Tyrosine is often sold as an herbal supplement. There are no regulated manufacturing standards in place for many herbal compounds and some marketed supplements have been found to be contaminated with toxic metals or other drugs. Herbal/health supplements should be purchased from a reliable source to minimize the risk of contamination.

L-Tyrosine is the precursor of the catecholamines; alterations in the availability of L-tyrosine to the brain can influence the synthesis of both dopamine and norepinephrine in experimental animals and probably in humans. In animals, stress increases the release of catecholamines, which can result in the depletion of their levels, an effect that can be corrected by giving L-tyrosine. L-Tyrosine does not seem to enhance the release of catecholamines when neurons are firing at their basal rates, but it does when firing rates are increased by stress. This is the basis for studying the effect of L-tyrosine on the stress response of humans.

L-Tyrosine is a non-essential amino acid synthesized in the body from the amino acid phenylalanine. It is a precursor from which the body makes dopamine, which is then converted to norepinephrine and then to epinephrine. This formula provides 1200 mg of L-tyrosine, along with vitamin C for its role as a cofactor in neurotransmitter production. Tyrosine is ideally taken on an empty stomach or two hours before a protein-containing meal to avoid competition with other amino acids for absorption.

 References

[1] Deijen J B , Orlebeke J F . Effect of tyrosine on cognitive function and blood pressure under stress.[J]. Brain Research Bulletin, 1994, 33(3):319-23.
[2] M. Giovannini, E. Verduci, E. Salvatici, L. Fiori, E. Riva Phenylketonuria: dietary and therapeutic challenges J. Inherit. Metab. Dis., 30 (2) (2007), pp. 145-152.
[3] A. Mostad, H.M. Nissen, C. Romming Acta Chem. Scand., 26 (1972), p. 3819.
[4] A. Rajput, A.H. Rajput Parkinson’s disease management strategies Expert Rev. Neurother., 6 (1) (2006), pp. 91-99.
[5] M.S. Chow, B.E. Eser, S.A. Wilson, K.O. Hodgson, B. Hedman, P.F. Fitzpatrick, E.I. Solomon Spectroscopy and kinetics of wild-type and mutant tyrosine hydroxylase: mechanistic insight into O2 activation, J. Am. Chem. Soc., 131 (2009), pp. 7685-7698.