What does phenylalanine mean?
Phenylalanine is one of the nine essential amino acids, meaning that humans must obtain it through food rather than make it themselves. It is one of the raw materials from which the body builds proteins and is also converted into tyrosine, a precursor of dopamine, norepinephrine, epinephrine, melanin, and thyroid hormones. Phenylalanine is found in protein-rich foods such as meat, eggs, dairy products, nuts, seeds, and legumes. Its chemical name derives from the phenyl group, a carbon-based ring structure, and its role as an amino acid. Because the body's handling of phenylalanine is genetically regulated, disorders such as phenylketonuria can result when that process is impaired. In ordinary nutrition and biochemistry, the unqualified term generally denotes the naturally occurring L-phenylalanine.
nounPhenylalanine is an essential amino acid and a building block of proteins, obtained from the diet because the human body cannot synthesize it. It is also used in the body's production of several important molecules, including neurotransmitters, melanin, and the thyroid hormones.
- An essential amino acid that serves as a protein-building block and is converted into tyrosine and other biologically important compounds.
"A balanced diet should provide enough dietary phenylalanine to support normal protein synthesis."
"Phenylalanine is one of the nine essential amino acids that must be supplied by the human diet."
"The analysis detected unusually high phenylalanine levels in the newborn's blood."
The plural is uncommon; biochemical and nutritional discussions normally use the singular form.
"The researchers compared the phenylalanines isolated from two different samples."
Phenylalanine is one letter in the genetic code, but a small change in how the body handles it can have major lifelong effects.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does phenylalanine come from?
The word combines “phenyl,” from the Greek phēn, meaning “more” or “related,” via the naming of benzene-derived groups, with “alanine,” the name of the simpler amino acid alanine. The compound was named during the development of modern organic chemistry and biochemistry as researchers identified amino acids with distinctive side chains. Its suffix reflects its close chemical relationship to alanine rather than a direct historical transformation of the older word.
Related word forms
How phenylalanine is actually used
The term is most common in biochemistry, nutrition, medicine, and genetics. In nutritional and medical contexts, it usually refers to the naturally occurring L-isomer unless another form is specified.
Easily confused with phenylalanine
Alanine is a different essential amino acid, while phenylalanine is distinguished by its benzene-containing side chain.
Tyrosine is a different amino acid that is produced from phenylalanine in the body and serves as the precursor of several neurotransmitters.