Protein phosphatases are pest containing proteins.

Protein phosphatases are required for removing phosphoryl groups in proteins involved in many physiological processes. Investigation of these enzymes for regions rich in proline (P), glutamic acid (E), serine (S) and threonine (T), called PEST regions showed that greater than 85% of the phosphatases investigated contained these regions. These regions are believed to be signals for degradation and could possibly serve as regulators of the intracellular localization and catalytic activity via limited proteolysis or as conditional signals for rapid degradation of these proteins by the ATP/ubiquitin-dependent and/or the ATP non-ubiquitin dependent proteolytic pathway. Many of these phosphatases were also found to contain a pentapeptide sequence biochemically related to the KFERQ motif which targets proteins for lysosomal degradation which suggest that several pathways may exist for the degradation of protein phosphatases.