Abbrev. Y Tyr
Full Name Tyrosine
Side chain type hydrophilic
pKr (R) 10.46
Side chain -CH2-C6H4OH
Hydro- phobic yes
Aromatic or Aliphatic Aromatic
van der Waals volume 141
Codon UAU, UAC
Occurrence in proteins (%) 3.2
Remarks: Behaves similarly to phenylalanine and tryptophan (see phenylalanine). Precursor of melanin, epinephrine, and thyroid hormones.
Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in cheese), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells to synthesize proteins. It has a phenol side chain.
Tyrosine is converted to DOPA by Tyrosine hydroxylase, an enzyme.
It plays a key role in signal transduction, since it can be tagged with a phosphate group (phosphorylated) by protein kinases to alter the functionality and activity of certain enzymes. (In its phosphorylated state, it is sometimes referred to as phosphotyrosine.) Tyrosine is also precursor to the thyroid hormones thyroxine and triiodothyronine, the pigment melanin, and the biologically-active catecholamines dopamine, norepinephrine and epinephrine.
In Papaver somniferum, the opium poppy, it is used to produce morphine.
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