fenylalaninin

Fenylalanin, known in English as phenylalanine, is an essential amino acid required for human health. It occurs in two enantiomeric forms, L- and D-; the L-form is the one incorporated into body proteins, while the D-form is not used for protein synthesis. Its chemical name is 2-amino-3-phenylpropanoic acid, and its molecular formula is C9H11NO2.

As an essential amino acid, phenylalanine must be obtained from the diet because the human body cannot synthesize it. In the body, it serves as a precursor to tyrosine through the action of the enzyme phenylalanine hydroxylase, with tetrahydrobiopterin as a cofactor. Tyrosine then contributes to the synthesis of catecholamines (dopamine, norepinephrine, epinephrine) and melanin, in addition to its role in protein construction. Phenylalanine itself is also incorporated directly into proteins during translation.

Dietary sources of phenylalanine include high-protein foods such as meat, fish, eggs, dairy products, soy, legumes, nuts, and seeds. The amount present in foods varies with protein content, and total daily intake depends on age, body weight, and overall protein needs.

Phenylketonuria (PKU) is a genetic disorder characterized by insufficient activity of phenylalanine hydroxylase or related metabolic defects, leading to elevated phenylalanine levels that can affect brain development if untreated. Newborn screening programs detect PKU early, and management typically involves a diet low in phenylalanine, with careful monitoring and, in some cases, restriction of phenylalanine-containing additives such as aspartame.

In industry, phenylalanine is used in pharmaceutical synthesis and, as part of aspartame, contributes to the flavor of some zero- or low-calorie products.