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{{dablink|Tyrosine kinases are a subclass of Protein_kinase, see there for the principles of protein Phosphorylation}} A '''tyrosine kinase''' is an Enzyme that can transfer a Phosphate group from ATP to a Tyrosine residue in a Protein. Tyrosine kinases are a subgroup of the larger class of Protein_kinases. Phosphorylation of proteins by kinases is an important mechanism in Signal_transduction for regulation of enzyme activity. The tyrosine kinases are divided into two groups; those that are cytoplasmic proteins and the transmembrane receptor-linked kinases. In humans, there are 32 cytoplasmic protein tyrosine kinases ({{EC number|}}) and 58 receptor-linked protein-tyrosine kinases ({{EC number|}}). The Hormones and Growth_factors that act on cell surface tyrosine kinase-linked receptors are generally growth-promoting and function to stimulate Cell_division (e.g., Insulin, Insulin-like_growth_factor_1, Epidermal_growth_factor). == General properties == There are over 100 3D structures of tyrosine kinases available at the Protein_Data_Bank. An example is PDB 1IRK, the crystal structure of the tyrosine kinase domain of the human Insulin_receptor. The first non-receptor tyrosine kinase identified was the ''v-src'' oncogenic protein. Most animal cells contain one or more members of the ''Src'' family of tyrosine kinases. A chicken sarcoma virus was found to carry mutated version of the normal cellular Src gene. The mutated v-''src'' gene has lost the normal built-in inhibition of enzyme activity that is characteristic of cellular SRC (c-''src'') genes. SRC family members have been found to regulate many cellular processes. For example, the T-cell antigen receptor leads to intracellular signalling by activation of ''Lck'' and ''Fyn'', two proteins that are structurally similar to ''Src''. Most tyrosine kinases have an associated Protein_tyrosine_phosphatase. ==''Abl''== {{protein | Name = v-abl Abelson murine leukemia viral oncogene homolog 1 | caption = | image = | width = | HGNCid = 76 | Symbol = ABL1 | AltSymbols = ABL | EntrezGene = 25 | OMIM = 189980 | RefSeq = NM_007313 | UniProt = P00519 | PDB = | ECnumber = | Chromosome = 9 | Arm = q | Band = 34.1 | LocusSupplementaryData = }} ''Abl'' (Abelson leukemia virus protein, Chromosome 9q34) is an important tyrosine kinase. This gene is fused with the ''bcr'' gene in a Philadelphia_chromosome, the characteristic abnormality in Chronic_myelogenous_leukemia (CML) and rarely in some other Leukemia forms. The ''bcr-abl'' transcript is also a ''tyrosine kinase'', which activates mediators of the Cell_cycle regulation system, leading to a clonal Myeloproliferative_disorder. The ''bcr-abl'' protein can be inhibited with the agent imatinib mesylate, which occupies the ''TK'' domain and inhibits ''bcr-abl''s influence on the cell cycle. == ''c-kit'' (CD117) == {{protein | Name = v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog | caption = | image = | width = | HGNCid = 6342 | Symbol = KIT | AltSymbols = | EntrezGene = 3815 | OMIM = 164920 | RefSeq = NM_000222 | UniProt = P10721 | PDB = | ECnumber = | Chromosome = 4 | Arm = q | Band = 11 | LocusSupplementaryData = -q12 }} This CD molecule is the membrane receptor for Stem_cell_factor (SCF), also known as "steel factor" or "c-kit ligand". Steel factor is a Polypeptide that activates Bone_marrow precursors of a number of Blood_cells, but its receptor is also present on other cells. ''C-kit'' mutations in the Interstitial_cells_of_Cajal in the Digestive_tract are probably the key to Gastrointestinal_stromal_tumors (GISTs), and explain the efficacy of Imatinib in the management of these rare malignancies. Cluster_of_differentiation (CD) molecules are markers on the cell surface, as recognized by specific sets of antibodies, used to identify the cell type, stage of differentiation and activity of a cell. ==Sources== * {{OMIM|189980}} (ABL) * {{OMIM|151410}} (BCR) ==See also== * Receptor_tyrosine_kinase Category:Tyrosine_kinases Category:EC_2.7.10 Ar:تيروزين_كيناز De:Tyrosinkinase Es:Tirosincinasa