protein serine/threonine phosphatase

{{Short description|Class of enzymes}}

{{Infobox enzyme

| Name = protein-serine/threonine phosphatase

| EC_number = 3.1.3.16

| CAS_number = 9025-75-6

| GO_code =

| image = 5muf.jpg

| width = 270

| caption = Protein serine/threonine phosphatase dodecamer, Human

}}

The enzyme protein serine/threonine phosphatase (EC 3.1.3.16; systematic name protein-serine/threonine-phosphate phosphohydrolase){{cite journal | vauthors = Shi Y |title=Serine/threonine phosphatases: mechanism through structure |journal=Cell |volume=139 |issue=3 |pages=468–84 |date=October 2009 |pmid=19879837 |doi=10.1016/j.cell.2009.10.006 |doi-access=free }} is a form of phosphoprotein phosphatase that acts upon phosphorylated serine/threonine residues:

[a protein]-serine/threonine phosphate + H₂O = [a protein]-serine/threonine + phosphate

Serine and threonine phosphates are stable under physiological conditions, so a phosphatase enzyme has to remove the phosphate to reverse the regulation signal. Ser/Thr-specific protein phosphatases are regulated partly by their location within the cell and by specific inhibitor proteins.

Serine and threonine are amino acids which have similar side-chain compositions that contain a hydroxyl group and thus can be phosphorylated by enzymes called serine/threonine protein kinases. The addition of the phosphate group can be reversed by enzymes called serine/threonine phosphatases. The addition and removal of phosphate groups regulates many cellular pathways involved in cell proliferation, programmed cell death (apoptosis), embryonic development, and cell differentiation.