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Enolase-phosphatase E1 (ENOPH1) belongs to the MasA family of the HAD (halo-acid dehalogenase)-like hydrolase superfamily. ENOPH1 is a bifunctional enzyme which demonstrates both phosphatase and atypical enolase activities. ENOPH1 has a significant role in the ubiquitous methionine salvage pathway which is a biochemical pathway found in all organisms that regulate methionine levels in the cell.

Phosphoglycolate phosphatase (PGP) is discovered in all tissues including red cells, lymphocytes and cultured fibroblasts (at protein level). PGP is most active in skeletal muscle and cardiac muscle. The catalytic activity of PGP is 2-phosphoglycolate + H2O = glycolate + phosphate. Diseases associated with PGP include tardive dyskinesia and polycystic kidney disease.

N-acylneuraminate-9-phosphatase (NANP) belongs to the haloacid dehalogenase (HAD) family and is responsible for dephosphorylating N-acylneuraminate 9-phosphate to form N-acylneuraminate (N-acylneuraminate 9-phosphate + H2O = N-acylneuraminate + phosphate). The catalytic activity of NANP is relies on the presence of magnesium and is inhibited by vanadate and calcium, which is typical of the HAD phosphatase family.

Human Phosphoserine phosphatase (hPSP) is an important enzyme in the phosphorylated pathway of serine biosynthesis, which contributes a major portion of the endogenous L-serine. Similar to known L-3-phosphoserine phosphatases, it catalyzed the Mg2+-dependent hydrolysis of L-phosphoserine and an exchange reaction between L-serine and L-phosphoserine. Recently, its complex structures reveal that the open-closed environmental change of the active site, generated -helical bundle domain, is important to substrate by local rearrangement of the recognition and hydrolysis.

PHPT1 is a member of the Janus protein familyand is 125 amino acid long. PHPT1 appears as a monomer in the cytoplasm and is an EDTA-insensitive phosphohistidine phosphatase. Overexpression of PHPT1 resolts in specific phosphohistidine phosphatase activity towards phosphopeptide I, with no activity detected towards phosphotyrosine, phosphothreonine and phosphoserine peptides.

Acid Phosphatase-2, also known as ACP2 is composed of two subunits, Alpha & beta, and is chemically as well as genetically distinct from red cell acid phosphatase. ACP2 belongs to a family of distinct isoenzymes which hydrolyze orthophosphoric monoesters to alcohol and phosphate. In addition, Acid phosphatase deficiency is caused by mutations in the ACP2-beta subunit as well as ACP3-alpha subunit genes.

Dual specificity phosphatase 18 (DUSP18) belongs to the dual-specificity phosphatase (DSP) family, which catalyzes dephosphorylation of phosphotyrosine and phosphothreonine residues. DUSP18 has a preferential enzymatic activity for phosphorylated tyrosine residues over threonine residues, in addition DUSP18 dephosphorylates p-nitrophenyl phosphate (pNPP) in vitro. Furthermore, DUSP18 is inhibited by iodoarectic acid and is activated by manganese ions. DUSP18 is extensively expressed with the highest levels in the liver, brain, ovary and testis.

PPP1CC is vital for cell division and takes part in the regulation of protein synthesis, muscle contractility and glycogen metabolism. Additionally, PPP1CC has a role in long-term synaptic plasticity and regulation of ionic conductance, and has a significant role in dephosphorylating substrates such as the postsynaptic density-associated Ca2+/calmodulin dependent protein kinase II.

PPP1R14A is a phosphorylation-dependent inhibitor of smooth muscle myosin phosphatase. Inhibition of PPP1R14A results to increased myosin phosphorylation and enhances smooth muscle contraction in the absence of increased intracellular Ca(2+) concentration. Myosin phosphatase can reverse MYL (myosin light chain) phosphorylation to induce a state of relaxation. However, during agonist-induced contraction at constant Ca2+ concurrent inhibition of myosin phosphatase leads to increases in MYL phosphorylation and tension. These calcium-independent increases in myosin phosphorylation and tension are termed calcium sensitization.
Human pregnancy is characterized by the increases of PKN1 expression and CPI-17 phosphorylation in the myometrium. PPP1R14A is mapped to chromosome 19q13.13-q13.2.
PPP1R14A binds directly to protein kinase C and casein kinase I.
PPP1R14A siRNA decreased the level of merlin phosphorylation and consequently Ras and ERK activity in human tumor cell lines.
PKC/CPI-17 mediated pathway in histamine, triggeres cytoskeletal rearrangements causing lung microvascular barrier compromise.

Tartrate-resistant acid phosphatase type 5 (ACP5) is involved in osteopontin and bone sialoprotein dephosphorylation. ACP5 is an iron containing glycoprotein which catalyzes the conversion of orthophosphoric monoester to alcohol and orthophosphate. ACP5 expression seems to increase in some pathological states such as Gaucher and Hodgkin diseases, the hairy cell, the B-cell, and the T-cell leukemias. ACP5 is the most basic of the acid phosphatases and is the only form not inhibited by L(+)-tartrate.

PHPT1 is a member of the Janus protein familyand is 125 amino acid long. PHPT1 appears as a monomer in the cytoplasm and is an EDTA-insensitive phosphohistidine phosphatase. Overexpression of PHPT1 resolts in specific phosphohistidine phosphatase activity towards phosphopeptide I, with no activity detected towards phosphotyrosine, phosphothreonine and phosphoserine peptides.

Placental alkaline phosphatase also known as PLAP is a membranal siaglycoprotein enzyme typicallyfoundin high concentration in syncytiotrophoblasts in the placenta amid the 3th trimester of gestation. The expression of PLAP was at firstconsidered to be onlyin the term placenta, though, a human PLAP-like variant has been found,thathas more than 85% homology with PLAP itself. PLAP is expressed strictly in normal term placenta, endocervix & fallopian tube and in ovarian and proximal gastrointestinal tumors. It is also widely expressed in germ cell tumors and more recently found in seminomas.

DUSP3 belongs to the dual specificity protein phosphatase subfamily which inactivates their target kinases by dephosphorylating both the phosphoserine/threonine and phosphotyrosine residues. DUSP3 negatively regulate members of the mitogen-activated protein kinase superfamily that are related to cellular proliferation and differentiation. DUSP3 is expressed in both breast and ovarian tissues and displays activity both for tyrosine-protein phosphate and serine-protein phosphate, but exhibits a strong preference toward phosphotyrosines, specifically dephosphorylates and inactivates ERK1 and ERK2.

Dual Specificity Phosphatase 26 (DUSP26) inhibits MAP kinase p38 by dephosphorylating it and inhibits p38-mediated apoptosis in anaplastic thyroid cancer cells. DUSP26 also induces activation of MAP kinase p38 and c-Jun N-terminal kinase. DUSP26 inactivates MAPK1 and MAPK3 which leads to dephosphorylation of heat shock factor protein 4 and a decrease in its DNA-binding activity.

Dual specificity phosphatase 13 (DUSP13) is a member of the protein-tyrosine phosphatase family. DUSP13 cooperates with protein kinases to control cell proliferation and differentiation. DUSP13 is engaged in the regulation of meiosis and/or differentiation of testicular germ cells in the course of spermatogenesis. DUSP13 demonstrates intrinsic phosphatase activity towards both phospho-seryl/threonyl and -tyrosyl residues of myelin basic protein, with similar specific activities in vitro.

PPP3R1 is a Ser/Thr-specific calcium and calmodulin-dependent protein phosphatase which takes a vital part in the T cell activation pathway. Calcineurin is composed of two subunits; calcineurin A (CnA) and calcineurin B (CnB). Dephosphorylation of the nuclear factor of activated T-cells (NF-AT) by Calcineurin is essential for NF-AT activation, nuclear translocation, and early gene expression in T-cells.

Alkaline Phosphatase Liver/Bone/Kidney (Alpl) is a part of the alkaline phosphatases family which comprises 4 related alkaline phosphatases. Alpl is a membrane-bound glycosylated enzyme which is not expressed in any particular tissue. Alpl takes part in skeletal mineralization.

PPP1R1A is an inhibitor of protein-phosphatase 1. IPP-1 protein plays important in hormonal control of glycogen metabolism. Hormones that elevate intracellular cAMP elevate IPP-1 activity. PPP1R1A activation caused cAMP to control over proteins that are not directly phosphorylated by PKA following a rise in intracellular calcium, IPP-1 is inactivated by calcineurin (PP2B). Multiple domains in IPP-1 target cellular PP1 complexes. PPP1R1A is a cellular regulator of eIF2 alpha phosphorylation.

Placental alkaline phosphatase (PLAP) is a membrane-associated siaglycoprotein enzyme normally present at high concentration in syncytiotrophoblasts within the placenta during the third trimester of gestation. The expression of PLAP was originally thought to be restricted to term placenta but a human PLAP-like variant has been described which shares more than 85% homology with PLAP itself. PLAP is expressed only in normal term placenta, endocervix and fallopian tube and also in ovarian and proximal gastrointestinal tumors. It is also commonly expressed in germ cell tumors and more recently described in seminomas.

Protein Phosphatase 1D (PPM1D) belongs to the PP2C family of Ser/Thr protein phosphatases whose members are negative regulators of cell stress response pathways. PPM1D is induced by tumor suppressor protein TP53/p53 in response to multiple environmental stresses. PPM1D is a negative regulator of the activity of p38 MAP kinase through which it reduces the phosphorylation of p53 and suppresses p53-mediated transcription and apoptosis. PPM1D is located in a chromosomal area which enlarges in breast cancer.

Protein Phosphatase 1, Regulatory Subunit 2 (PPP1R2) is an inhibitor of protein-phosphatase 1 which forms heterodimer with PP1. PPP1R2 is a part of the protein phosphatase inhibitor 2 family.

Dual Specificity Phosphatase 6, also known as DUSP6 belongs to the dual specificity protein phosphatase subfamily. DUSP6 is a Protein coding gene which inactivates MAP kinases. Various members of the family of dual specificity phosphatases show diverse tissue distribution, subcellular localization, and different modes of inducibility of their expression by extracellular stimuli.

PPP3R2 is a calcium-dependent, calmodulin stimulated serine/threonine protein phosphatase. In eukaryotes, the phosphorylation and dephosphorylation of proteins on serine and threonine residues is a crucial means of regulating a wide range of cellular functions including division, homeostasis and apoptosis. Ordinarily the protein phosphatase (PP) holoenzyme is a trimeric complex composed of a regulatory subunit, a variable subunit and a catalytic subunit.

Serine/Threonine-protein phosphatase PP1-alpha catalytic subunit (PPP1CA) is crucial for cell division, and participates in the regulation of glycogen metabolism, muscle contractility and protein synthesis. The PPP1CA protein may have a significant role in dephosphorylating substrates such as the postsynaptic density-associated Ca2+/calmodulin dependent protein kinase II.