Proteinphosphatases are enzymes that remove phosphate groups that have been attached to amino acid residues of proteins by protein kinases. The phosphates are important in signal transduction by regulating the proteins they are attached to. To reverse the regulatory effect, the phosphate has to be removed. This occurs on its own by hydrolysis or is mediated by protein phosphatases.
Serine and threonine phosphates are stable under physiological conditions, so a phosphatase has to remove the phosphate to reverse the regulation. There are four known groups:
