Kinases that phosphorylate protein tyrosine residues. These kinases play major roles in mitogenic signalling, and can be divided into two subfamilies: receptor tyrosine kinases, that have an extracellular ligand-binding domain, a single transmembrane domain, and an intracellular tyrosine kinase domain; and nonreceptor tyrosine kinases, which are soluble, cytoplasmic kinases. (Dictionary of Cell and Molecular Biology Online)