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Definition of Phenylalanine

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Phenylalanine: An essential amino acid. (The human body cannot make it so it is essential to the diet.) Phenylalanine that is ingested is largely transformed (hydroxylated) to form the amino acid tyrosine, which is used in protein synthesis. Too little phenylalanine curbs physical and intellectual growth. Too much phenylalanine, as in phenylketonuria (PKU), is highly toxic to the brain. Phenylanine was first isolated in 1879 and first synthesized in 1882. Symbol: Phe.

See also Phenylalanine hydroxylase deficiency; Phenylketonuria (PKU); Maternal phenylketonuria.

Reviewed on 12/11/2018

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