What are the functions of tyrosine kinase?

Tyrosine kinases are vital regulators of the signaling cascade, as they play key roles in processes including cell differentiation, cell-cell communication, metabolism, growth, and apoptosis in response to internal and external stimuli. These kinases can either promote or inhibit cellular proteins involved in apoptosis, or transcription factors and also protect against cell death. Additionally, these enzymes catalyze phosphorylation of specific tyrosine residues on protein substrates, utilizing ATP. These kinases act as signal transducers which regulate cell-to-cell communication by phosphorylating tyrosine residues on specific intracellular proteins. This phosphorylation helps to regulate enzyme activity and forms binding sites for the gathering of downstream signaling proteins. Protein tyrosine kinases are broken down into two classes: transmembrane receptor protein kinases and non receptor protein kinases. Transmembrane receptor protein kinases help to maintain the stability of receptor dimers as well as maintaining proper dimeric receptor conformation. Non-receptor protein kinases are able to relay intracellular signals derived from extracellular receptors. This mechanism is specific for pathways involved in activation, cellular growth, and differentiation.