Tyrosine-specific protein phosphatases (PTPase; EC 3.1.3.48) catalyse the removal of a phosphate group attached to a tyrosine residue, using a cysteinyl-phosphate enzyme intermediate.

PTPs are increasingly viewed as integral components of signal transduction cascades, despite less study and understanding compared to tyrosine kinases.

PTPs have been implicated in regulation of many cellular processes, including, but not limited to: PTP activity can be found in four protein families.

Ser/Thr and Tyr dual-specificity phosphatases are a group of enzymes with both Ser/Thr (EC 3.1.3.16) and tyrosine-specific protein phosphatase (EC 3.1.3.48) activity able to remove the serine/threonine or the tyrosine-bound phosphate group from a wide range of phosphoproteins, including a number of enzymes that have been phosphorylated under the action of a kinase.

Dual-specificity protein phosphatases (DSPs) regulate mitogenic signal transduction and control the cell cycle.