• Made from Phenylalanine, then transformed into 3 kinds of neurotransmitters.
    • A non-essential, protein-forming amino acid, is elevated.
  • Tyrosine is not found in large concentrations throughout the body, probably because it is rapidly metabolized.
  • Folic acid, copper, and vitamin C are cofactor nutrients of these reactions.
  • Tyrosine is also the precursor for hormones, thyroid, catechol estrogens and the major human pigment, melanin. While dopa is also an intermediate in the formation of melanin, different enzymes hydroxylase tyrosinase in melanocytes. Dopa decarboxylase, a pyridoxal phosphate-dependent enzyme, forms dopamine. Subsequent hydroxylation by dopamine β-oxidase then forms norepinephrine.
  • Tyrosine is an important amino acid in many proteins, peptides and even enkephalins, the body's natural pain reliever.
    • Occasionally, down-regulation of tyrosine transaminase and elevated urine tyrosine is a consequence of adrenocortical insufficiency provided that this condition does not also reduce uptake of dietary tyrosine.
    • The heptapeptide opioids dermorphin and deltophorin in the skin of South American tree frogs contain D-tyrosine and D-alanine.


    • An essential amino acid that is used to make tyrosine. Like tyrosine, it is the precursor of catecholamines (adrenalin-like substances) in the body (tyramine, dopamine, epinephrine, and norepinephrine).
    • Tyrosine is produced in cells by hydroxylating the essential amino acid phenylalanine. This relationship is much like that between cysteine and methionine. Half of the phenylalanine required goes into the production of tyrosine; if the diet is rich in tyrosine itself, the requirements for phenylalanine are reduced by about 50%.
    • Phenylalanine is structurally closely related to dopamine, epinephrine (adrenaline) and tyrosine.
    • L-phenylalanine can also be converted into L-tyrosine, another one of the DNA-encoded amino acids. L-tyrosine, in turn, is converted into L-DOPA, which is further converted into dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline). The latter three are known as the catecholamines.
    • Phenylalanine is better absorbed than tyrosine and may cause fewer headaches.
    • Phenylalanine hydroxylase converts phenylalanine to tyrosine.
    • Low phenylalanine diets have been prescribed for certain cancers with mixed results. Some tumors use more phenylalanine (particularly melatonin-producing tumors called melanoma). One strategy is to exclude this amino acid from the diet, i.e., a Phenylketonuria (PKU) diet (compliance is a difficult issue; it is hard to quantify and is under-researched). The other strategy is just to increase phenylalanine competing for amino acids, i.e., tryptophan, valine, isoleucine, and leucine, but not tyrosine.
  • Chronically high levels of phenylalanine are associated with at least four other inborn errors of metabolism including:
        • Hartnup Disorder, Hyperphenylalaninemia due to guanosine triphosphate cyclohydrolase deficiency, Tyrosinemia Type 2 (or Richner-Hanhart syndrome) and Tyrosinemia Type 3 (TYRO3).


    • The mechanism of L-tyrosine antidepressant activity can be accounted for by the precursor role of L-tyrosine in the synthesis of the neurotransmitters norepinephrine and dopamine. Elevated brain norepinephrine and dopamine levels are thought to be associated with antidepressant effects.


    • Has an energizing effect, useful for treating depression and lethargy.


    • Can raise blood pressure to dangerous levels, especially for those taking MAO inhibitors as antidepressants.
    • Valine and other branched amino acids, and possibly tryptophan and phenylalanine may reduce tyrosine absorption.


  • Some adults develop elevated tyrosine in their blood. This indicates a need for more vitamin C. More tyrosine is needed under stress, and tyrosine supplements prevent the stress-induced depletion of norepinephrine and can cure biochemical depression. However, tyrosine may not be good for psychosis. Many antipsychotic medications apparently function by inhibiting tyrosine metabolism.

Blood-Brain Barrier:

  • Tyrosine is an essential amino acid that readily passes the blood-brain barrier. Once in the brain, it is a precursor for the neurotransmitters dopamine, norepinephrine and epinephrine, better known as adrenaline. These neurotransmitters are an important part of the body's sympathetic nervous system, and their concentrations in the body and brain are directly dependent upon dietary tyrosine.


  • A number of genetic errors of tyrosine metabolism occur. Most common is the increased amount of tyrosine in the blood of premature infants, which is marked by decreased motor activity, lethargy, and poor feeding. Infection and intellectual deficits may occur. Vitamin C supplements reverse the disease.


    • Tyrosine is also a precursor of triiodothyronine and thyroxine.
    • Tyrosine forms both epinephrine and norepinephrine, and its iodination forms thyroid hormone.
    • free L-α-amino acids play an important role in metabolic processes like tyrosine in the formation of thyroid hormones.


  • Tyrosinemia may coexist with tyrosinuria and the most common cause is either vitamin B6 deficiency or pyridoxal 5-phosphate dysfunction, or weakness of the tyrosine transaminase enzyme and increased need for vitamin B6 or pyridoxal 5-phosphate.
  • Corresponding urine elevations of tyrosine are slight or mild, not severe. In severe cases or with acute tyrosinuria and tyrosinemia the condition is sometimes referred to as Tyrosinemia Type II or Richner-Hanhart syndrome. Most instances are of moderate degree and are corrected by vitamin B6 or pyridoxal 5-phosphate supplementation. Untreated or severe conditions may feature neurological disorders, behavioral problems, and hyperactivity (in children), photophobia, eye lesions or hazy corneas, and skin lesions in the form of hyperkeratotic plaques on elbows, knees, palms, and soles. Failure of vitamin B6 to clear the problem suggests a need for a low phenylalanine and low tyrosine diet.


  • L-dopa, which is directly used in Parkinson's, is made from tyrosine. Tyrosine, the nutrient, can be used as an adjunct in the treatment of Parkinson's. Peripheral metabolism of tyrosine necessitates large doses of tyrosine, however, compared to L-dopa.

Phenylacetic Acid (PAA) is elevated:

  • Some elevation of PAA may occur in the uncommon instances of phenylketonuria and with Type I tyrosinemia (tyrosinosis). With phenylketonuria, 2-hydroxyphenylacetate (2-HPAA) would be significantly elevated. An amino acid analysis also is helpful in diagnosing such conditions.

Genes SNP’s:

    • rs28934581 TH A733C G
    • rs28934580 TH G1010A//R337H T
    • rs2070762 TH T1090C G
    • rs7483056 TH T7517C A
    • rs6356 TH V112M T
    • rs28940881 TYR A5083G G
    • rs1393350 TYR G105007A A

L-Tyrosine Health Effects:

    • Anti depressant
    • Anti encephalopathic
    • Anti Parkinsonian
    • Anti phenylketonuric
    • Anti-ulcer
    • Cancer preventive
    • Monoamine precursor


    • In the liver, L-tyrosine is involved in a number of biochemical reactions, including protein synthesis and oxidative catabolic reactions. L-tyrosine that is not metabolized in the liver is distributed via the systemic circulation to the various tissues of the body.


    • Tyrosine is claimed to act as an effective antidepressant, however, results are mixed. Tyrosine has also been claimed to reduce stress and combat narcolepsy and chronic fatigue, however, these claims have been refuted by some studies.

Route of Exposure:

    • L-tyrosine is absorbed from the small intestine by a sodium-dependent active transport process.