Editing Tyrosine kinase (section)

== Function ==
Kinase is a large family of enzymes that are responsible for catalyzing the transfer of a phosphoryl group from a nucleoside triphosphate donor, such as ATP, to an acceptor molecule.<ref name="Lehninger_2008"/> Tyrosine kinases catalyze the phosphorylation of tyrosine residues in proteins.<ref name="Lehninger_2008">{{cite book | vauthors = Cox M, Nelson DR | title = Lehninger: Principles of Biochemistry | edition = fifth | publisher = W H Freeman & Co | year = 2008 | isbn = 978-1-4292-2416-1 }}</ref>  The phosphorylation of tyrosine residues in turn causes a change in the function of the protein that they are contained in.<ref name="Lehninger_2008"/>

Phosphorylation at tyrosine residues controls a wide range of properties in proteins such as enzyme activity, subcellular localization, and interaction between molecules.<ref name="Radha_1996"/> Furthermore, tyrosine kinases function in many [[signal transduction]] cascades wherein extracellular signals are transmitted through the [[cell membrane]] to the [[cytoplasm]] and often to the [[cell nucleus|nucleus]], where gene expression may be modified.<ref name="Radha_1996">{{cite journal | vauthors = Radha V, Nambirajan S, Swarup G | title = Association of Lyn tyrosine kinase with the nuclear matrix and cell-cycle-dependent changes in matrix-associated tyrosine kinase activity | journal = European Journal of Biochemistry | volume = 236 | issue = 2 | pages = 352–359 | date = March 1996 | pmid = 8612602 | doi = 10.1111/j.1432-1033.1996.00352.x | doi-access = free }}</ref>  Finally [[CD117#Role in cancer|mutations]] can cause some tyrosine kinases to become constitutively active, a nonstop functional state that may contribute to initiation or progression of cancer.

Tyrosine kinases function in a variety of processes, pathways, and actions, and are responsible for key events in the body. The receptor tyrosine kinases function in transmembrane signaling, whereas tyrosine kinases within the cell function in signal transduction to the nucleus.<ref name="Ruetten_1997">{{cite journal | vauthors = Ruetten H, Thiemermann C | title = Effects of tyrphostins and genistein on the circulatory failure and organ dysfunction caused by endotoxin in the rat: a possible role for protein tyrosine kinase | journal = British Journal of Pharmacology | volume = 122 | issue = 1 | pages = 59–70 | date = September 1997 | pmid = 9298529 | pmc = 1564904 | doi = 10.1038/sj.bjp.0701345 }}</ref> Tyrosine kinase activity in the nucleus involves cell-cycle control and properties of [[transcription factor]]s.<ref name="Radha_1996"/> In this way, in fact, tyrosine kinase activity is involved in [[mitogenesis]], or the induction of [[mitosis]] in a cell; proteins in the cytosol and proteins in the nucleus are phosphorylated at tyrosine residues during this process.<ref name="Radha_1996"/> Cellular growth and reproduction may rely to some degree on tyrosine kinase. Tyrosine kinase function has been observed in the [[nuclear matrix]], which comprises not the [[chromatin]] but rather the [[nuclear envelope]] and a “fibrous web” that serves to physically stabilize DNA.<ref name="Radha_1996"/> To be specific, [[LYN|Lyn]], a type of kinase in the [[Src (gene)|Src]] family that was identified in the nuclear matrix, appears to control the [[cell cycle]]. Src family tyrosine kinases are closely related but demonstrate a wide variety of functionality. Roles or expressions of Src family tyrosine kinases vary significantly according to cell type, as well as during cell growth and differentiation.<ref name="Radha_1996"/> Lyn and Src family tyrosine kinases in general have been known to function in signal transduction pathways.<ref name="Radha_1996"/> There is evidence that Lyn is localized at the cell membrane; Lyn is associated both physically and functionally with a variety of receptor molecules.<ref name="Radha_1996"/>

[[Fibroblast]]s – a type of cell that synthesizes the [[extracellular matrix]] and [[collagen]] and is involved in wound healing – that have been transformed by the [[polyomavirus]] possess higher tyrosine activity in the cellular matrix. Furthermore, tyrosine kinase activity has been determined to be correlated to [[cellular transformation]].<ref name="Radha_1996"/> It has also been demonstrated that phosphorylation of a middle-T antigen on tyrosine is also associated with cell transformation, a change that is similar to cellular growth or reproduction.<ref name="Radha_1996"/>

The transmission of mechanical force and regulatory signals are quite fundamental in the normal survival of a living organism. Protein tyrosine kinase plays a role in this task, too. A protein tyrosine kinase called [[PTK2|pp125]], also referred to as focal adhesion kinase (FAK) is likely at hand in the influence of cellular focal adhesions, as indicated by an immunofluorescent localization of FAK. Focal adhesions are macromolecular structures that function in the transmission of mechanical force and regulatory signals.<ref name="Schaller_1992">{{cite journal | vauthors = Schaller MD, Borgman CA, Cobb BS, Vines RR, Reynolds AB, Parsons JT | title = pp125FAK a structurally distinctive protein-tyrosine kinase associated with focal adhesions | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 89 | issue = 11 | pages = 5192–5196 | date = June 1992 | pmid = 1594631 | pmc = 49256 | doi = 10.1073/pnas.89.11.5192 | doi-access = free | bibcode = 1992PNAS...89.5192S }}</ref>

Cellular proliferation, as explained in some detail above, may rely in some part on tyrosine kinase.<ref name="Radha_1996"/> Tyrosine kinase function has been observed in the nuclear matrix. Lyn, the type of kinase that was the first to be discovered in the nuclear matrix, is part of Src family of tyrosine kinases, which can be contained in the nucleus of differentiating, calcium-provoked kertinocytes. Lyn, in the nuclear matrix, among the nuclear envelope and the “fibrous web” that physically stabilizes DNA, was found functioning in association with the matrix. Also, it appeared to be conditional to cell cycle.<ref name="Radha_1996"/> The contribution of the Lyn protein to the total tyrosine kinase activity within the nuclear matrix is unknown, however; because the Lyn was extracted only partially, an accurate measurement of its activity could not be managed.<ref name="Radha_1996"/> Indications, as such, are that, according to Vegesna ''et al.'' (1996), Lyn polypeptides are associated with tyrosine kinase activity in the nuclear matrix. The extracted Lyn was enzymatically active, offering support for this notion.

Yet another possible and probable role of protein tyrosine kinase is that in the event of circulatory failure and organ dysfunction caused by endotoxin in rats, where the effects of inhibitors [[tyrphostin]] and [[genistein]] are involved with protein tyrosine kinase.<ref name="Ruetten_1997"/>  Signals in the surroundings received by receptors in the membranes of cells are transmitted into the cell cytoplasm. Transmembrane signaling due to receptor tyrosine kinases, according to Bae ''et al.'' (2009), relies heavily on interactions, for example, mediated by the SH2 protein domain; it has been determined via experimentation that the SH2 protein domain selectivity is functional in mediating cellular processes involving tyrosine kinase. Receptor tyrosine kinases may, by this method, influence growth factor receptor signaling. This is one of the more fundamental cellular communication functions metazoans.<ref name="Dengjel_2009">{{cite journal | vauthors = Dengjel J, Kratchmarova I, Blagoev B | title = Receptor tyrosine kinase signaling: a view from quantitative proteomics | journal = Molecular BioSystems | volume = 5 | issue = 10 | pages = 1112–1121 | date = October 2009 | pmid = 19756300 | doi = 10.1039/b909534a | url = https://zenodo.org/record/895954 | archive-date = 2021-10-29 | access-date = 2019-09-06 | archive-url = https://web.archive.org/web/20211029080430/https://zenodo.org/record/895954 | url-status = live }}</ref>