Phenylalanine

The amino acid Phenylalanine exists in two forms, the D- and L- forms. L-Phenylalanine(LPA, C9H12NO2) is a neutral amino acid found in proteins, coded for by DNA. Its mirror image, D-phenylalanine (DPA), can be synthesized artificially.

L-phenylalanine is used in the human body, where it is an essential amino acid. L-Phenylalanine can also be converted into tyrosine. Tyrosine is converted into L-dopa, norepinephrine, and epinephrine. D-phenylalanine can only be converted into phenylethylamine.

The genetic disorder phenylketonuria is an inability to metabolize phenylalanine.

The synthesized mix DL-Phenylalanine (DLPA), which is a combination of the D- and L- forms, is used as a nutritional supplement.

What does phenylalanine do?

L-phenylalanine (LPA) serves as a building block for the various proteins that are produced in the body. LPA can be converted to L-tyrosine (another amino acid) and subsequently to L-dopa, norepinephrine, and epinephrine. LPA can also be converted (through a separate pathway) to phenylethylamine, a substance that occurs naturally in the brain and appears to elevate mood.

D-phenylalanine (DPA) is not normally found in the body and cannot be converted to L-tyrosine, L-dopa, or norepinephrine. As a result, DPA is converted primarily to phenylethylamine (the potential mood elevator). DPA also appears to influence certain chemicals in the brain that relate to pain sensation.

DLPA is a mixture of LPA and its mirror image DPA. DLPA (or the D- or L-form alone) has been used to treat depression.DPA may be helpful for some people with Parkinson’s disease and has been used to treat chronic pain—including pain from osteoarthritis and rheumatoid arthritis—with both positive and negative results. No research has evaluated the effectiveness of DLPA on rheumatoid arthritis.

Where is phenylalanine found?

LPA is found in most foods that contain protein. DPA does not normally occur in food. However, when phenylalanine is synthesized in the laboratory, half appears in the L-form and the other half in the D-form. These two compounds can also be synthesized individually, but it is more expensive to do so. The combination supplement (DLPA) is often used because of the lower cost and because both components exert different health-enhancing effects.

<< Back

Menu

Structure of Amino Acids
Amino Acid Properties

Classes of Amino Acids
Amino Acid Disorders Screening
Functions and Non-functions in proteins