Dual phosphatases

The classical PTPs can be subdivided into receptorlike PTPs and nonreceptor, cytosolic PTPs. The second category of PTPs are broadly defined as dual specificity phosphatases (DSPs), which dephosphorylate pSer/ pThr as well as pTyr. MAP kinase phosphatases (MKPs) ( MAP kinase cascades) and PTEN are examples of DSP family members. Remarkably, PTEN also has lipid phosphatase activity that is specific for phosphatidylinositol-3,4,5-trisphosphate generated in response to the actions of PI3K. Finally, the class of low molecular mass (LM-) PTPs and that of CDC25 PTPs accomplish the cells repertoire of PTPs (Fig. 3). 

Mitogen-activated protein kinase phosphatases are dual-function protein phosphatases 401... 

Mitogen-activated protein kinase phosphatases are dual-function protein phosphatases. Just as the MAPK kinases (e.g. MEKs) are unique as dual-functioning kinases in that they phosphorylate MAPKs on threonine and tyrosine residues, there are unique dual-function ing protein phosphatases that reverse the phosphorylation and activation of MAPKs [43], Such MAPK phosphatases (MKPs) were first identified as a product of vaccinia virus (VH1) and later found in all eukaryotic cells. There are now numerous members of this VH1 family of dual-functioning protein phosphatases. 

Some members of this family have been shown to mediate the dephosphorylation of MAPKs under physiological conditions. Others dephosphorylate Cdc-2 and related CDKs. However, relatively little is known to date about the regional distribution of these dual-functioning phosphatases in the brain and the specific function these enzymes serve in the regulation of neuronal signal transduction. Considerable interest has focused on one particular MAPK phosphatase, which can be induced very rapidly, at the level of gene transcription, in target cells in response to cellular activation [44]. 

Keyse, S. M. An emerging family of dual specificity MAP kinase phosphatases. Biochim. Biophys. Acta 1265 152-160, 1995. 

DSPc Dual specificity phosphatase, catalytic domain E(MFP)B 5(5) 10(10) 1VHR... 

Phosphorylation of serine, threonine, or tyrosine residues by protein kinases, and their dephosphorylation by protein phosphatases, are critical mechanisms by which information-relaying signals are transduced in eukaryotic cells. Although protein kinases are by no means an eukaryotic invention (see Leonard et al., 1998 for details), the large numbers of protein kinases in eukaryotes (118 in. S . cerevisiae and 435 in C. elegans (Chervitz et al., 1998)) reflect their importance in a multitude of diverse cellular processes. Eukaryotes have evolved signaling pathways that exploit the dual state of an amino acid, dependent on its state of phosphorylation, both as a signaling mechanism and as a means of colocalization of molecules within multimolecular complexes. 

Helgason, CD., Kalberer, C.P., Damen, J.E., Chappel, S.M., Pineault, N., Krystal, G., and Humphries, R.K., 2000, A dual role forSrc homology 2 domarn-contarning inositol-5-phosphatase (SHIP) in immunity aberrant development and enhanced function ofB lymphocytes in ship -/- mice. J Exp Med. 191 5 781-5794. 

Fig. 1. A simplified flow chart for dual-color bright-field in situ hybridization (BISH) assays using horseradish peroxidase (HRP) and/or alkaline phosphatase (AP)-based immunological signal detections.

Fig. 7.16. The dual function of protein kinases and protein phosphatases. Phosphorylation of proteins (PI, P2) can fix the latter into an active or inactive state. In the case of PI, protein kinases have an activating effect and protein phosphatases are inactivating the reverse is trne for P2.

Fig. 1. Dual nucleic acid detection. The target DNAs (A and B) are denatured and hybridized with complementary DNA probes labeled with biotin (Bio ), or digoxigenm (Dig ). Biotin and digoxigenm residues are detected, respectively, with avidin peroxidase (red) and antibody to digoxigenin labeled with alkaline phosphatase (blue).

Denu, J.M. and J.E. Dixon. 1995. A catalytic mechanism for the dual-specific phosphatases. Biochemistry 92 5910-5914. 

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