DL-m-Tyrosine (3-hydroxy-DL-phenylalanine) is a synthetic amino acid and analog of tyrosine, primarily utilized in biochemical and pharmacological research. It acts as a competitive inhibitor of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of catecholamine neurotransmitters such as dopamine, norepinephrine, and epinephrine. This inhibition allows researchers to deplete catecholamine levels, facilitating studies on their roles in brain function, stress responses, mood regulation, and neurological disorders including depression, anxiety, schizophrenia, and Parkinson's disease.

In pharmaceutical development, DL-m-Tyrosine is employed in the creation of enzyme inhibitors and receptor ligands to explore therapeutic interventions for catecholamine-related conditions. Its applications extend to biotechnology for the synthesis of modified peptides and proteins. While L-tyrosine is more common in nutritional supplements for cognitive support and stress relief, DL-m-Tyrosine has been investigated in preliminary studies for potential benefits in enhancing mental alertness and mood under stress, though clinical evidence remains limited. It is not typically used in general food or sports supplements due to its inhibitory effects.