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Tyrosine phosphorylation is the addition of a phosphate (PO 4 3−) group to the amino acid tyrosine on a protein. It is one of the main types of protein phosphorylation . This transfer is made possible through enzymes called tyrosine kinases .
Tyrosine kinases belong to a larger class of enzymes known as protein kinases which also attach phosphates to other amino acids such as serine and threonine. Phosphorylation of proteins by kinases is an important mechanism for communicating signals within a cell (signal transduction) and regulating cellular activity, such as cell division.
Tyrosine phosphorylation is a fast, reversible reaction, and one of the major regulatory mechanisms in signal transduction. Cell growth, differentiation, migration, and metabolic homeostasis are cellular processes maintained by tyrosine phosphorylation. The function of protein tyrosine kinases and protein-tyrosine phosphatase counterbalances ...
Dimerization of RTKs leads to autophosphorylation of tyrosine in the catalytic core of the dimer, and finally stimulation of the tyrosine kinase activity and cell signaling. [21] It is thus an example of a trans-autophosphorylation reaction, where one receptor subunit of the dimer phosphorylates the other subunit.
Tyrosine phosphorylation is considered to be one of the key steps in signal transduction and regulation of enzymatic activity. Phosphotyrosine can be detected through specific antibodies . Tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation . [ 17 ]
As a consequence, maintaining an appropriate level of protein tyrosine phosphorylation is essential for many cellular functions. Tyrosine-specific protein phosphatases (PTPase; EC 3.1.3.48 ) catalyse the removal of a phosphate group attached to a tyrosine residue, using a cysteinyl-phosphate enzyme intermediate.
Phosphorylation can occur on serine, threonine and tyrosine side chains (in other words, on their residues) through phosphoester bond formation, on histidine, lysine and arginine through phosphoramidate bonds, and on aspartic acid and glutamic acid through mixed anhydride linkages.
[8] [9] [10] Exact mechanisms of this phenomenon are as of yet not elucidated. Other non-catalytic tyrosine-phosphorylated receptors carry a conserved inhibitory motif that, when phosphorylated, results in the inhibition of the signaling pathway via recruitment of phosphatases, namely SHP-1, SHP-2 and SHIP1. This serves not only for inhibition ...