phenylalanine

noun

phe·​nyl·​al·​a·​nine ˌfe-nᵊl-ˈa-lə-ˌnēn How to pronounce phenylalanine (audio)
ˌfē-
: an essential amino acid C9H11NO2 that is converted in the normal body to tyrosine

Examples of phenylalanine in a Sentence

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Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The disease leads to toxic levels of phenylalanine, a building block of protein, in the blood. — Emily Mullin, Wired News, 9 Jan. 2026 Treatment for this condition usually involves a low phenylalanine diet and avoiding certain foods. — Sean Mowbray, Discover Magazine, 22 Apr. 2025 Contains phenylalanine and tryptophan, amino acids with antidepressant properties. — Lindsey Desoto, Health, 5 June 2025 The other six essential amino acids required to build and repair muscle are histidine, lysine, methionine, phenylalanine, threonine, and tryptophan. — Shimite Obialo, Forbes.com, 26 May 2026 See All Example Sentences for phenylalanine

Word History

Etymology

International Scientific Vocabulary

First Known Use

circa 1883, in the meaning defined above

Time Traveler
The first known use of phenylalanine was circa 1883

Rhymes for phenylalanine

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Browse Nearby Words

phenylacetaldehyde
phenylalanine
phenylate
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Cite this Entry

“Phenylalanine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/phenylalanine. Accessed 7 Jul. 2026.

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Medical Definition

phenylalanine

noun
phe·​nyl·​al·​a·​nine ˌfen-ᵊl-ˈal-ə-ˌnēn, ˌfēn- How to pronounce phenylalanine (audio)
: an essential amino acid C9H11NO2 that is obtained in its levorotatory L-form by the hydrolysis of proteins (as lactalbumin), that is essential in human nutrition, and that is converted in the normal body to tyrosine
—abbreviation Phe see phenylketonuria, phenylpyruvic acid

More from Merriam-Webster on phenylalanine

Britannica.com: Encyclopedia article about phenylalanine

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