phenylalanine

noun

phe·​nyl·​al·​a·​nine ˌfe-nᵊl-ˈa-lə-ˌnēn 

ˌfē-

: 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

That’s because those born with PKU have inherited a gene mutation that prevents an enzyme called phenylalanine hydroxylase (PAH) from converting phenylalanine into stuff that your body can use. —Bruce Y. Lee, Forbes, 18 Feb. 2024

For example, the primary treatment for phenylketonuria (PKU) is limiting the intake of foods that contain an amino acid called phenylalanine such as meat, dairy, nuts and tofu. —Bruce Y. Lee, Forbes, 18 Feb. 2024

The committee further noted that, when consumed, aspartame quickly breaks down in the gastrointestinal tract into three common metabolites: phenylalanine, aspartic acid, and methanol. —Beth Mole, Ars Technica, 17 July 2023

With a deficiency of the enzyme, phenylalanine and its metabolites can build up in the blood and damage the brain cells. —Dr. Keith Roach, oregonlive, 15 Aug. 2023

August 1974: The FDA receives objections that phenylalanine in aspartame could lead to convulsions and intellectual disabilities. —Ananya Bhattacharya, Quartz, 14 July 2023

For now, the only strong health advisory against aspartame is for people with phenylketonuria (PKU) who can't break down the protein phenylalanine which is found in aspartame. —Stephanie Brown, Verywell Health, 13 July 2023

High-quality protein is any protein that contains all of the nine essential amino acids (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) that our bodies don’t make on their own. —USA TODAY, 2 July 2023

Of those, 60 percent—or nine people—saw more than 20 percent reduction in their phenylalanine levels at either the one-week or two-week mark, which was measured via blood draws. —WIRED, 7 Nov. 2022

Word History

Etymology

International Scientific Vocabulary

First Known Use

circa 1883, in the meaning defined above

Medical Definition

phenylalanine

noun

phe·​nyl·​al·​a·​nine ˌfen-ᵊl-ˈal-ə-ˌnēn, ˌfēn- 

: 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