Tyrosine

Tyrosine (L‑tyrosine) is a non‑essential, aromatic amino acid that serves as a building block for proteins and a precursor to several biologically active compounds. These include:

• The neurotransmitters dopamine, norepinephrine, and epinephrine
• Thyroid hormones
• Melanin

In humans, tyrosine is synthesized from phenylalanine or obtained directly from the diet. It supports neuro‑chemical and metabolic processes critical for:

• Cognition
• Stress response
• Pigmentation

• IUPAC name: (2S)-2‑amino‑3‑(4‑hydroxyphenyl)propanoic acid.
• Molecular formula: C₉H₁₁NO₃; Molar mass: 181.19 g mol⁻¹.
• Structure: An α‑amino acid with a phenolic (‑OH) substituent at the para position of the aromatic ring, giving it both hydrophilic (carboxyl, amino) and aromatic characteristics. The p‑hydroxy group confers antioxidant activity and serves as the site for iodination in thyroid hormone synthesis. It is a zwitterion at physiological pH, with a pKa₁ ≈ 2.2 (carboxyl) and pKa₂ ≈ 9.1 (amino). Solubility: ~0.45 g L⁻¹ in water at 20 °C; soluble in dilute acid and alkaline solutions.

Dietary sources include high‑protein foods:

• Dairy (cheese, yogurt)
• Meat
• Fish
• Eggs
• Soy products
• Legumes
• Nuts
• Seeds

Commercial supplements are produced either by:

• fermentation of genetically engineered Escherichia coli
• chemical synthesis from phenylacetate

Both methods yield high‑purity L‑tyrosine (>98 %). Extraction from natural protein hydrolysates is also used but may contain mixed amino‑acids. Quality considerations:

• certificate of analysis (COA) confirming enantiomeric purity (L‑form)
• absence of heavy metals
• compliance with USP/NF or EFSA standards

For clinical use, GMP‑certified production and third‑party testing (e.g., USP, NSF) are recommended to ensure purity and minimize contaminants.