phenylalanint

Phenylalanint appears to be a misspelling of phenylalanine. Phenylalanine is an essential amino acid in humans and other animals. It is one of the 20 standard amino acids used to build proteins. The L-stereoisomer is incorporated into proteins, while the D-stereoisomer is not used in human protein synthesis. The chemical formula is C9H11NO2 and its side chain is a benzyl group, making it one of the hydrophobic, aromatic amino acids.

Within the body, phenylalanine serves as a precursor to tyrosine, which is produced by the enzyme phenylalanine hydroxylase, using tetrahydrobiopterin as a cofactor. Tyrosine in turn is used to synthesize catecholamines (dopamine, norepinephrine, epinephrine) and the pigment melanin, as well as thyroid hormones via tyrosine. Phenylalanine can be obtained from dietary protein and is present in meat, dairy, eggs, soy, nuts, and some grains. The body cannot synthesize phenylalanine; daily intake must come from food.

Phenylalanine metabolism is disrupted in phenylketonuria (PKU), a genetic disorder caused by loss of function of phenylalanine hydroxylase. Without adequate conversion to tyrosine, phenylalanine accumulates and can cause intellectual disability and other symptoms if untreated. Newborn screening identifies PKU, and management includes restricting phenylalanine intake and supplementing tyrosine. People with PKU often manage diet with medical foods.

Phenylalanine is also present in the artificial sweetener aspartame, requiring caution for individuals with PKU.