Is protein phosphorylation reversible?

Yes, protein phosphorylation is reversible. 

Phosphorylation is the addition of a phosphate group from an energy-rich molecule such as ATP to a protein, which can alter its function, activity, or location within the cell. This process is catalyzed by the enzyme protein kinase. 

This process can be reversed through dephosphorylation, which removes the phosphate group from the protein. This process is catalyzed by the enzyme phosphatase. 

The reversible nature of protein phosphorylation is essential for regulating cellular processes such as signal transduction, gene expression, and metabolism. By adding or removing phosphate groups from proteins, cells can adjust their activity rapidly and efficiently in response to changing environmental conditions or signals.