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
Example Sentences
Recent Examples on the Web He was born with phenylketonuria (PKU), the build-up of amino acid called phenylalanine in the body which can cause learning disabilities. 
Eric Walden, The Salt Lake Tribune, 10 Aug. 2022 The test offered a way to detect high levels of phenylalanine, the amino acid that builds up in PKU. Mark Johnson, jsonline.com, 29 Apr. 2022 If a person had large amounts of phenylalanine in the blood, the disease's signature, bacteria would proliferate; otherwise the bacteria would be held in check. Mark Johnson, jsonline.com, 29 Apr. 2022 With this knowledge, the family started their child on treatment with a specialized diet including low levels of phenylalanine. Wendy Chung, Scientific American, 30 Apr. 2021 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, 24 Dec. 2019 Aspartame does break down into methanol and phenylalanine. Kat Eschner, Smithsonian, 27 Jan. 2017 See More
Eric Walden, The Salt Lake Tribune, 10 Aug. 2022 The test offered a way to detect high levels of phenylalanine, the amino acid that builds up in PKU. Mark Johnson, jsonline.com, 29 Apr. 2022 If a person had large amounts of phenylalanine in the blood, the disease's signature, bacteria would proliferate; otherwise the bacteria would be held in check. Mark Johnson, jsonline.com, 29 Apr. 2022 With this knowledge, the family started their child on treatment with a specialized diet including low levels of phenylalanine. Wendy Chung, Scientific American, 30 Apr. 2021 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, 24 Dec. 2019 Aspartame does break down into methanol and phenylalanine. Kat Eschner, Smithsonian, 27 Jan. 2017 See More 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