Abbreviated: Tyr or Y
Molecular formula: C9H11NO3
pKa: 2.20(carboxyl), 9.11(amino), 10.07(R Group)
Physiological Roles
The R group of tyrosine is polar. Its codons are UAC and UAU. Tyrosine is classified as a non essential amino acid, it can be synthesised. But if you want more in your diet though tyrosine can be found in high protein foods such as chicken, fish, peanuts, milk, cheese and yogurt.
Tyrosine is plays important roles in the nervous system. One of its fates is that it is converted into catecholamines. Catecholamines are molecules that have a catechol nucleus consisting of benzene with two hydroxyl side groups, and a side-chain amine. In the nervous system the catecholamines are the always important dopamine, norepinephrine, and epinephrine, all neurotransmitters. (King 2012)
This occurs by tyrosine first being converted into DOPA (3,4-dihydrophenylalanine) by a tyrosine hydroxylase. From there a DOPA carboylase will convert DOPA into dopamine which in turn can be synthesised into norepinephrine and epinephrine.
In bacteria protein-tyrosine kinases have been found to phosphorylate protein substrates, including RNA polymerase sigma factors, UDP-glucose dehydrogenases and single-stranded DNA-binding proteins, all important in cellular life (Mijakovic et al). Because of this particular activity new antimicrobial drugs are being made to target the tyrosine kinases and the phosphorylation of certain endogenous proteins catalyzed by specific tyrosine kinases (Cozzone).
Synthesis
Tyrosine synthesis begins with a chorismate. The chorismate is converted to prephenate by chorismate pyruvatemutase.
From there the prephenate is acted on by prephenate dehydrogenase (NADP+)and NAD+ to make a carbon dioxide, NADPH and 4-hydroxyphenylpyruvate.
The final step occurs when L-glutamate and 4-hydroxyphenylpyruvate are acted on by a tyrosine transaminase to make 2-oxoglutuate and L-tyrosine (Enzyme Database)
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