Question

Tyrosine kinases that are not receptors, however they have the same activity because they phosphorylate tyrosine residues, but they are cytosolic enzymes instead of intracellular components of a transmembrane receptor?

Answer 1

Non-receptor tyrosine kinases are cytosolic enzymes that phosphorylate tyrosine residues on target proteins within the cell, instead of being part of a transmembrane receptor, leading to downstream cellular responses.

Step-by-step explanation:

The student is referring to non-receptor tyrosine kinases that play a role in cellular response mechanisms similar to receptor tyrosine kinases but are located in the cytoplasm rather than embedded in the cell membrane. Unlike receptor tyrosine kinases, which have an extracellular domain for ligand binding and dimerize upon activation, leading to autophosphorylation of intracellular tyrosine residues, non-receptor tyrosine kinases are already present in the cytoplasm and can phosphorylate other proteins to transmit a signal within the cell.

When stimulated by various signaling pathways, non-receptor tyrosine kinases can phosphorylate specific tyrosine residues on target proteins within the cell, effectuating a downstream cellular response. This mechanism is pivotal in cellular signaling and can influence a multitude of cellular functions, including gene expression, cell division, and metabolism. An example of such non-receptor tyrosine kinase activity could be the Src family of kinases, which are known for their role in signaling pathways inside cells.