phenylalanine

Phenylalanine is an essential α-amino acid found naturally in many protein-rich foods and used as a dietary supplement. It exists in three forms: L-phenylalanine (the natural form incorporated into proteins), D-phenylalanine (a synthetic variant), and DL-phenylalanine (a racemic mixture). Phenylalanine is a precursor for tyrosine and subsequently for the neurotransmitters dopamine, norepinephrine, and epinephrine. Its mechanisms of action include serving as a substrate for neurotransmitter synthesis—potentially contributing to antidepressant effects—and stimulating the release of satiety hormones such as cholecystokinin (CCK) and peptide YY (PYY), which may regulate appetite. Phenylalanine also increases insulin and glucagon secretion, influencing glucose metabolism. In the brain, L-phenylalanine acts as an antagonist at NMDA receptor glycine binding sites and AMPA receptor glutamate binding sites; it can inhibit neurotransmitter release at glutamatergic synapses at high concentrations[1][6][8]. D-Phenylalanine has been proposed to treat chronic pain by inhibiting enkephalinase[5]. Phenylketonuria is a genetic disorder that impairs phenylalanine metabolism.

Other names

L-phenylalanineD-phenylalanineDL-phenylalaninePheF