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Tyrosine

L-tyrosine is an amino acid that the body synthesizes from phenylalanine, another amino acid. Vitamin B6 is necessary for conversion of L-tyrosine into neuro transmitters including L-dopa, Dopamine, norepinephrine and epinephrine. L-Tyrosine is a precursor for dopamine, norepinephrine, thryoxin, catacholestrogens, melanin, and enkephalines. L-tyrosine can be used as an antidepressant, a growth hormone promoter, an appetite suppressant, or an antioxidant. Trosine occurs in proteins that are part of signal transduction processes. It functions as a receiver of phosphate groups that are transferred by way of protein kinases (so-called receptor tyrosine kinases). Phosphorylation of the hydroxyl group changes the activity of the target protein. A tyrosine residue also plays an important role in photosynthesis. In chloroplasts (photosystem II), it acts as an electron donor in the reduction of oxidized chlorophyll. In this process, it undergoes deprotonation of its phenolic OH-group. This radical is subsequently reduced in the photosystem II by the four core manganese cluster. Protein tyrosine phosphorylation is an important molecular switching mechanism that regulates a variety of cellular functions including cell proliferation, differentiation, and activation. Tyrosine phosphorylation is not only an essential part of the signal transduction mediated by various growth factor receptors, but it is also involved in intracellular signal transduction and nuclear cell cycle regulation. Disturbances of these processes are known to be causes of cancer.

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