Phenylalanine

Phenylalanine is an essential aromatic amino acid incorporated into proteins and converted in humans into tyrosine. Its aromatic side chain contributes to protein structure and molecular interactions.

Phenylalanine hydroxylase: Phenylalanine hydroxylase is the enzyme that converts phenylalanine into tyrosine. This enzyme catalyzes phenylalanine’s main metabolic conversion in humans.
Amino acid: An amino acid is an organic molecule with amino and carboxyl groups; many serve as protein building blocks. Phenylalanine is one of the standard amino acids used to build proteins.
Essential amino acid: An essential amino acid is an amino acid humans must obtain from the diet because they cannot synthesize enough of it. Humans cannot synthesize phenylalanine’s carbon skeleton in sufficient amounts.
Tryptophan: Tryptophan is an essential aromatic amino acid and a precursor to serotonin, melatonin, and niacin. It is another essential aromatic amino acid used in proteins.
Tetrahydrobiopterin: Tetrahydrobiopterin is a cofactor used by enzymes that hydroxylate aromatic amino acids. Phenylalanine hydroxylase requires this cofactor to make tyrosine.
Aromaticity: Aromaticity is the stabilization of certain cyclic, conjugated molecules by delocalized electrons. Phenylalanine’s benzyl side chain contains an aromatic phenyl ring.
Dietary protein: Dietary protein is protein consumed in food and digested into amino acids and small peptides. It is a major source of phenylalanine for human metabolism.
Leucine: Leucine is an essential branched-chain amino acid that also serves as a signal regulating protein synthesis. Both leucine and phenylalanine are essential amino acids, but their side chains differ in structure.
Tyrosine: Tyrosine is an aromatic amino acid used in proteins and as a precursor to several signaling molecules. It is the direct product of phenylalanine hydroxylation.
Chirality: Chirality is the property of an object or molecule that makes it distinguishable from its mirror image. Protein-incorporated phenylalanine has the L configuration at its alpha carbon.

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