Protein tyrosine phosphatases (EC 3.1.3.48, systematic name protein-tyrosine-phosphate phosphohydrolase) are a group of enzymes that remove phosphate groups from phosphorylatedtyrosine residues on proteins:
Protein tyrosine (pTyr) phosphorylation is a common post-translational modification that can create novel recognition motifs for protein interactions and cellular localization, affect protein stability, and regulate enzyme activity. As a consequence, maintaining an appropriate level of protein tyrosine phosphorylation is essential for many cellular functions. Tyrosine-specific protein phosphatases (PTPase; EC3.1.3.48) catalyse the removal of a phosphate group attached to a tyrosine residue, using a cysteinyl-phosphate enzyme intermediate. These enzymes are key regulatory components in signal transduction pathways (such as the MAP kinase pathway) and cell cycle control, and are important in the control of cell growth, proliferation, differentiation, transformation, and synaptic plasticity.[1][2][3][4]
Dual-specificity phosphatases (dTyr and dSer/dThr) dual-specificity protein-tyrosine phosphatases. Ser/Thr and Tyr dual-specificity phosphatases are a group of enzymes with both Ser/Thr (EC3.1.3.16) and tyrosine-specific protein phosphatase (EC3.1.3.48) 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.
LMW (low-molecular-weight) phosphatases, or acid phosphatases, act on tyrosine phosphorylated proteins, low-MW aryl phosphates and natural and synthetic acyl phosphates.[17][18]
The class II PTPs contain only one member, low-molecular-weight phosphotyrosine phosphatase (LMPTP).
The Class III PTPs contains three members, CDC25 A, B, and C
Class IV
These are members of the HAD fold and superfamily, and include phosphatases specific to pTyr and pSer/Thr as well as small molecule phosphatases and other enzymes.[19] The subfamily EYA (eyes absent) is believed to be pTyr-specific, and has four members in human, EYA1, EYA2, EYA3, and EYA4. This class has a distinct catalytic mechanism from the other three classes.[20]
By location
Based on their cellular localization, PTPases are also classified as:
Receptor-like, which are transmembrane receptors that contain PTPase domains.[21] In terms of structure, all known receptor PTPases are made up of a variable-length extracellular domain, followed by a transmembrane region and a C-terminalcatalyticcytoplasmic domain. Some of the receptor PTPases contain fibronectin type III (FN-III) repeats, immunoglobulin-like domains, MAM domains, or carbonic anhydrase-like domains in their extracellular region. In general, the cytoplasmic region contains two copies of the PTPase domain. The first seems to have enzymatic activity, whereas the second is inactive.
All PTPases, other than those of the EYA family, carry the highly conserved active site motif C(X)5R (PTP signature motif), employ a common catalytic mechanism, and possess a similar core structure made of a central parallel beta-sheet with flanking alpha-helices containing a beta-loop-alpha-loop that encompasses the PTP signature motif.[23] Functional diversity between PTPases is endowed by regulatory domains and subunits.
Low-molecular-weight phosphotyrosine protein phosphatase
Structure of a low-molecular-weight phosphotyrosine protein phosphatase.[24]
Individual PTPs may be expressed by all cell types, or their expression may be strictly tissue-specific. Most cells express 30% to 60% of all the PTPs, however hematopoietic and neuronal cells express a higher number of PTPs in comparison to other cell types. T cells and B cells of hematopoietic origin express around 60 to 70 different PTPs. The expression of several PTPS is restricted to hematopoietic cells, for example, LYP, SHP1, CD45, and HePTP.[28] The expression of PTPN5 is restricted to the brain, and differs between brain regions, with no expression in the cerebellum.[29][30][31]
References
^Dixon JE, Denu JM (2018). "Protein tyrosine phosphatases: mechanisms of catalysis and regulation". Curr Opin Chem Biol. 2 (5): 633–41. doi:10.1016/S1367-5931(98)80095-1. PMID9818190.
^Sun JP, Zhang ZY, Wang WQ (2017). "An overview of the protein tyrosine phosphatase superfamily". Curr Top Med Chem. 3 (7): 739–48. doi:10.2174/1568026033452302. PMID12678841.
^Barford D, Das AK, Egloff MP (2021). "The structure and mechanism of protein phosphatase s: insights into catalysis and regulation". Annu. Rev. Biophys. Biomol. Struct. 27 (1): 133–64. doi:10.1146/annurev.biophys.27.1.133. PMID9646865.
