Category: Natural chemicals



Introduction and description

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Tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid.   Tyrosine, can be synthesized in the body from phenylalanine.  The conversion of phe to tyr is catalyzed by the enzyme phenylalanine hydroxylase.

The word "tyrosine" is from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese.

Uses in the body

In dopaminergic cells in the brain, tyrosine is converted to L-DOPA by the enzyme tyrosine hydroxylase (TH). TH is the rate-limiting enzyme involved in the synthesis of the neurotransmitter dopamine. Dopamine can then be converted into other catecholamines, such as norepinephrine (noradrenaline) and epinephrine (adrenaline).   So, as one can see, it may be called ‘non-essential’ its role in the body is essential and relates to numerous hormonal activity.

The thyroid hormones triiodothyronine (T3) and thyroxine (T4) in the colloid of the thyroid also are derived from tyrosine.  Tyrosine is also the precursor to the pigment melanin.  Tyrosine (or its precursor phenylalanine) is needed to synthesize the benzoquinone structure which forms part of coenzyme Q10.

In Taiwanese infants with tyrosine hydroxylase deficiency [the enzyme that converts tyrosine to L-DOPA and dopamine], researchers observed fetal distress during the perinatal period, and generalized tremour as their first observed neurologic sign at age 3 months. All presented “brisk reflexes, hypokinesia, rigidity, distal chorea, and athetosis”.  Long-term neurologic outcomes revealed two children who demonstrated slightly low intelligence quotients, three with mild to moderate psychomotor retardation, and one died of respiratory failure.  PMID:  22264700


Tyrosine  is found in many high-protein food products such as chicken, turkey, fish, milk, yogurt, cottage cheese, cheese, peanuts, almonds, pumpkin seeds, sesame seeds, soy products, lima beans, avocados, and bananas. For example, the white of an egg has about 250 mg per egg, while lean beef/lamb/pork/salmon/chicken/turkey contains about 1000 mg per 3 ounces (85 g) portion.

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