Tyrosine phosphorylation

Tyrosine Phosphorylation is a post-translational modification of proteins that plays a crucial role in cellular processes such as cell division, growth, and signal transduction pathways. It is a reversible process mediated by the action of two types of enzymes: protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs).

Overview

Tyrosine phosphorylation involves the addition of a phosphate group to the hydroxyl group of a tyrosine residue in a protein. This process is catalyzed by protein tyrosine kinases. The reverse process, dephosphorylation, involves the removal of the phosphate group and is catalyzed by protein tyrosine phosphatases.

Role in Cellular Processes

Tyrosine phosphorylation is involved in the regulation of a wide variety of cellular processes. It plays a key role in signal transduction pathways, where it acts as a switch to turn on or off certain cellular functions. It is also involved in the regulation of cell division and growth, and abnormalities in tyrosine phosphorylation can lead to diseases such as cancer.

Protein Tyrosine Kinases

Protein tyrosine kinases are enzymes that catalyze the transfer of a phosphate group from ATP to a tyrosine residue in a protein. There are two main types of PTKs: receptor tyrosine kinases, which are located at the cell surface and are activated by the binding of a ligand, and non-receptor tyrosine kinases, which are located inside the cell.

Protein Tyrosine Phosphatases

Protein tyrosine phosphatases are enzymes that catalyze the removal of a phosphate group from a phosphorylated tyrosine residue. They play a crucial role in the regulation of tyrosine phosphorylation, acting as a counterbalance to the action of PTKs.

Abnormalities and Disease

Abnormalities in tyrosine phosphorylation can lead to a variety of diseases. Overactivity of PTKs, for example, can lead to uncontrolled cell growth and division, a hallmark of cancer. On the other hand, underactivity of PTPs can also lead to excessive tyrosine phosphorylation and disease.

See Also

• Phosphorylation
• Protein Kinase
• Signal Transduction