Phosphorylation and Dephosphorylation
- Phosphorylation is the addition of a phosphate group (PO₄³⁻) to a protein or other organic molecule by protein kinases. This modification can alter the activity, localization, and interaction of proteins with other molecules, effectively turning them "on" or "off" or modulating their function in other ways.
- Dephosphorylation, the removal of a phosphate group, is performed by protein phosphatases and generally reverses the effects of phosphorylation, though the context and specific outcomes can vary.
Protein Kinases
Protein kinases are enzymes that catalyze the transfer of a phosphate group from a high-energy molecule, like ATP, to specific substrates. They are broadly classified into two main groups:
- 1. Serine/Threonine Kinases: These kinases phosphorylate the hydroxyl group of serine or threonine residues in proteins. Examples include PKA (Protein Kinase A), PKC (Protein Kinase C), and MAPK (Mitogen-Activated Protein Kinases).
- 2. Tyrosine Kinases: They specifically phosphorylate tyrosine residues in proteins. This class can be further divided into receptor tyrosine kinases (e.g., EGFR, VEGFR) and non-receptor tyrosine kinases (e.g., Src, Abl).