Medical Definition of tyrosine kinase
: any of a group of enzymes of protein kinase that catalyze the transfer of a phosphate group from ATP to a tyrosine residue in a protein’s side chain ◆Some tyrosine kinases are enzymes that act as cell membrane receptors by binding to extracellular ligands and activating intracellular signaling pathways, while others are enzymes that act in those pathways by regulating intracellular processes. <Other targeted agents that have been evaluated in phase 2 clinical trials for the treatment of hepatocellular carcinoma include tyrosine kinase inhibitors of the epidermal growth factor receptor …—Josep M. Llovet et al., The New England Journal of Medicine, 24 July 2008>
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