phe·​nyl·​al·​a·​nine | \ ˌfe-nᵊl-ˈa-lə-ˌnēn How to pronounce phenylalanine (audio) , ˌfē- \

Definition of phenylalanine

: an essential amino acid C9H11NO2 that is converted in the normal body to tyrosine

Examples of phenylalanine in a Sentence

Recent Examples on the Web In the 1960s microbiologist Robert Guthrie developed a test for phenylketonuria (PKU), a genetic disorder that causes the amino acid phenylalanine to build up in the body. Tanya Lewis, Scientific American, "23 and Baby," 24 Dec. 2019 Aspartame does break down into methanol and phenylalanine. Kat Eschner, Smithsonian, "‘Aspartame Causes Cancer’ Was a Classic Internet Hoax," 27 Jan. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'phenylalanine.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of phenylalanine

circa 1883, in the meaning defined above

History and Etymology for phenylalanine

International Scientific Vocabulary

Keep scrolling for more

Learn More about phenylalanine

Time Traveler for phenylalanine

Time Traveler

The first known use of phenylalanine was circa 1883

See more words from the same year

Statistics for phenylalanine

Cite this Entry

“Phenylalanine.” Dictionary, Merriam-Webster, Accessed 25 Oct. 2020.

Keep scrolling for more

More Definitions for phenylalanine


phe·​nyl·​al·​a·​nine | \ ˌfen-ᵊl-ˈal-ə-ˌnēn, ˌfēn- How to pronounce phenylalanine (audio) \

Medical Definition of phenylalanine

: 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 Encyclopedia article about phenylalanine

Comments on phenylalanine

What made you want to look up phenylalanine? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

Namesakes Word Quiz

  • a citrus fruit possibly named after a person
  • Which of the following is a fruit named after a Moroccan seaport?
Spell It

Can you spell these 10 commonly misspelled words?

Syn City

Test Your Knowledge - and learn some interesting things along the way.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!