L-tyrosine (Tyr)

L-tyrosine is a non-essential, proteinogenic amino acid that serves as a critical precursor for several physiologically important molecules, including catecholamine neurotransmitters (dopamine, norepinephrine, and epinephrine), thyroid hormones, and the pigment melanin (PubChem, CID 6057). It is synthesized endogenously from phenylalanine by the enzyme phenylalanine hydroxylase (StatPearls, Tyrosine). In clinical practice, L-tyrosine is primarily relevant in the management of metabolic disorders such as phenylketonuria (PKU), where it becomes an essential amino acid, and tyrosinemia, where its metabolic pathway is disrupted (NORD, Tyrosinemia). While not a therapeutic target in the traditional sense (like a receptor or enzyme), its levels are pharmacologically modulated, and it is used as a dietary supplement to support cognitive function under stress (NIH, Dietary Supplement Fact Sheets). Drugs like nitisinone target the enzymes involved in tyrosine catabolism to prevent the accumulation of toxic metabolites (DrugBank, DB00517). Additionally, L-tyrosine can interact with medications such as MAOIs, potentially leading to hypertensive crises, and may compete with Levodopa for transport into the central nervous system (Mayo Clinic).

Other names

(S)-2-Amino-3-(4-hydroxyphenyl)propanoic acid4-hydroxyphenylalanineL-p-TyrosineY

L-tyrosine serves as a metabolic substrate for the synthesis of catecholamines, thyroid hormones, and melanin (PubMed, PMID 2736402). It is converted to L-DOPA by tyrosine hydroxylase, which is the rate-limiting step in the production of dopamine, norepinephrine, and epinephrine (Wikipedia, Tyrosine). Pharmacological modulation of tyrosine levels is achieved by inhibiting catabolic enzymes like 4-hydroxyphenylpyruvate dioxygenase (DrugBank, DB00517).