Phosphorylation and dephosphorylation are two types of enzyme catalyzing reactions that involve phosphate groups. They are counterparts of each other. Both reactions are reversible and occur at specific sites on the surface of a protein. Both, phosphorylation and dephosphorylation, are important posttranslational modifications of native proteins, and both play key roles in intracellular signal transduction cascades and switching the enzymatic activity.