Editing Protein phosphatase (section)

==Sub-types==
Phosphatases can be subdivided based upon their substrate specificity. 
 
{| class="wikitable"
|-
! '''Class'''
! '''Example'''
! '''Substrate'''
! '''Reference'''
|-
| [[Tyrosine-specific phosphatase]]s
| [[PTP1B]]
| Phosphotyrosine
| <ref>{{cite journal | vauthors = Zhang ZY | title = Protein tyrosine phosphatases: structure and function, substrate specificity, and inhibitor development | journal = Annual Review of Pharmacology and Toxicology | volume = 42 | pages = 209–34 | year = 2002 | pmid = 11807171 | doi = 10.1146/annurev.pharmtox.42.083001.144616 }}</ref>
|-
| [[Serine]]-/[[threonine]]-specific phosphatases
| PP2C ([[PPP2CA]])
| Phosphoserine/-threonine
| <ref>{{cite journal | vauthors = Mumby MC, Walter G | title = Protein serine/threonine phosphatases: structure, regulation, and functions in cell growth | journal = Physiological Reviews | volume = 73 | issue = 4 | pages = 673–99 | date = October 1993 | pmid = 8415923 | doi = 10.1152/physrev.1993.73.4.673 }}</ref>
|-
| Dual specificity phosphatases
| VHR, [[DUSP1]]–[[DUSP28]]
| Phosphotyrosine/-serine/-threonine
| <ref>{{cite journal | vauthors = Camps M, Nichols A, Arkinstall S | title = Dual specificity phosphatases: a gene family for control of MAP kinase function | journal = FASEB Journal | volume = 14 | issue = 1 | pages = 6–16 | date = January 2000 | pmid = 10627275 | url = http://www.fasebj.org/cgi/pmidlookup?view=long&pmid=10627275 | doi=10.1096/fasebj.14.1.6| doi-access = free | s2cid = 17135681 }}</ref> 
|-
| [[Histidine]] phosphatase
| PHP
| Phospho-Histidine
| <ref>{{cite book |doi=10.1385/1-59745-267-X:247 |chapter=Expression of Protein Histidine Phosphatase in ''Escherichia coli'', Purification, and Determination of Enzyme Activity |title=Protein Phosphatase Protocols |year=2006 |last1=Bäumer |first1=Nicole |last2=Mäurer |first2=Anette |last3=Krieglstein |first3=Josef |last4=Klumpp |first4=Susanne |series=Methods in Molecular Biology |volume=365 |pages=247–260 |pmid=17200567 |isbn=1-59745-267-X }}</ref>
|}

===Serine/threonine PP (PPM/PPP) families===
{{main|Protein serine/threonine phosphatase}}
Protein Ser/Thr phosphatases were originally classified using biochemical assays as either, type 1 (PP1) or type 2 (PP2), and were further subdivided based on metal-ion requirement (PP2A, no metal ion; PP2B, Ca<sup>2+</sup> stimulated; PP2C, Mg<sup>2+</sup> dependent) (Moorhead et al., 2007). The protein Ser/Thr phosphatases PP1, PP2A and PP2B of the PPP family, together with PP2C of the PPM family, account for the majority of Ser/Thr PP activity in vivo (Barford et al., 1998). In the brain, they are present in different subcellular compartments in neuronal and glial cells, and contribute to different neuronal functions.

===PPM===
The PPM family, which includes PP2C and pyruvate dehydrogenase phosphatase, are enzymes with Mn<sup>2+</sup>/Mg<sup>2+</sup> metal ions that are resistant to classic inhibitors and toxins of the PPP family. Unlike most PPPs, PP2C exists in only one subunit but, like PTPs, it displays a wide variety of structural domains that confer unique functions. In addition, PP2C does not seem to be evolutionarily related to the major family of Ser/Thr PPs and has no sequence homology to ancient PPP enzymes. The current assumption is that PPMs evolved separately from PPPs but converged during evolutionary development.

===Class I: Cys-based PTPs===
Class I PTPs constitute the largest family. They contain the well-known classical receptor (a) and non-receptor PTPs (b), which are strictly tyrosine-specific, and the DSPs (c) which target Ser/Thr as well as Tyr and are the most diverse in terms of substrate specificity.

===Class III: Cys-based PTPs===
The third class of PTPs contains three cell cycle regulators, CDC25A, CDC25B and CDC25C, which dephosphorylate CDKs at their N-terminal, a reaction required to drive progression of the cell cycle. They are themselves regulated by phosphorylation and are degraded in response to DNA damage to prevent chromosomal abnormalities.

===Class IV: Asp-based DSPs===
The haloacid dehalogenase (HAD) superfamily is a further PP group that uses Asp as a nucleophile and was recently shown to have dual-specificity. These PPs can target both Ser and Tyr, but are thought to have greater specificity towards Tyr. A subfamily of HADs, the Eyes Absent Family (Eya), are also transcription factors and can therefore regulate their own phosphorylation and that of transcriptional cofactor/s, and contribute to the control of gene transcription. The combination of these two functions in Eya reveals a greater complexity of transcriptional gene control than previously thought . A further member of this class is the RNA polymerase II C-terminal domain phosphatase. While this family remains poorly understood, it is known to play important roles in development and nuclear morphology.