The Importance of Phenylalanine

For amino acids, compounds that are all chiral (with the exception of glycine with a H side chain), biochemists use the L and D nomenclature. This system is a practical way of avoiding ambiguity in representing the stereochemistry of molecules that have several asymmetric centers.^[1]

All naturally occurring proteins from all living organisms consist of L amino acids and phenylalanine is one of them.^[1] Phenylalanine is an important amino acid our body does not produce but provides it from food. There are three forms in which phenylalanine can be found:

• L-phenylalanine, the natural form found in proteins
• D-phenylalanine (made in laboratory)
• DL-phenylalanine, a combination of the 2 forms.^[2]

This amino acid can be changed from the body into “tyrosine, another amino acid that's needed to make proteins, brain chemicals, including L-dopa, epinephrine, and norepinephrine, and thyroid hormones”. ^[2]

Phenylalanine can be used to treat depression. Different symptoms can be noticed in people that have phenylalanine deficiency. Confusion, lack of energy, depression, decreased alertness, memory problems, and lack of appetite are some of the symptoms associated to lack of phenylalanine.^[2]

A genetic disorder called phenylketonuria (PKU) is caused from the inability of the body to process phenylalanine. Severe intellectual disability can be caused by increased levels of this amino acid. A screening test for PKU testes this disorder in babies during the first 48-72 hours of their life so that the problem can be treated early. Phenylketonuria is treated with low-protein diets that include fruits and vegetables and exclude all products with phenylalanine content.^[3]

D-phenylalanine can be used to treat chronic pain and improve some of the symptoms of Parkinson’s disease. L-phenylalanine can be used to increase the effect of UVA radiation for people with vitiligo, a disease that causes irregular loss of skin color. In addition, phenylalanine is thought to be effective in treating depression. However, more research is needed to confirm this hypothesis.^[2]

References:

1.     “Stereochemistry of Amino Acids.” Biowiki.ucdavis.edu. Accessed October 31, 2014. http://biowiki.ucdavis.edu/Biochemistry/Proteins/Structure_and_Properties_of_Amino_Acids/Stereochemistry_of_Amino_Acids.

2.     “Phenylalanine.” University of Maryland Medical Center. Accessed October 31, 2014. http://umm.edu/health/medical/altmed/supplement/phenylalanine.

3.     “Phenylketonuria.” Text. Accessed October 31, 2014. http://www.nlm.nih.gov/medlineplus/phenylketonuria.html.

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