A phosphatase is an
enzymethat removes a phosphate groupfrom its substrateby hydrolysing phosphoric acidmono esters into a phosphate ionand a molecule with a free hydroxylgroup (see dephosphorylation). This action is directly opposite to that of phosphorylases and kinases, which attach phosphate groups to their substrates by using energetic molecules like ATP. A common phosphatase in many organisms is alkaline phosphatase.
Phosphatases can be categorised into two main categories:
Cysteine-dependent Phosphatases (CDPs) and metallo-phosphatases (which are dependent on metal ions in their active sites for activity).
CDPs catalyse the hydrolysis of a phosphoester bond via a phospho-cysteine intermediate [Barford, D. Molecular mechanisms of the protein serine/threonine phosphatases, (1996) "Trends Bioch Sci",21, 11, pp407] .The free
cysteine nucleophileforms a bond with the phosphorusatom of the phosphate moiety, and the P-O bond linking the phosphate group to the tyrosine is protonated, either by a suitably positioned acidic amino acidresidue (Asp in the diagram below) or a water molecule. The phospho-cysteine intermediate is then hydrolysed by another water molecule, thus regenerating the active site for another dephosphorylation reaction.
Metallo-phosphatases (eg PP2C) co-ordinate 2 catalytically essential metal ions within their active site. There is currently some confusion of the identity of these metal ions, as successive attempts to identify them yield different answers. There is currently evidence that these metals could be
Magnesium, Manganese, Iron, Zinc, or any combination thereof. It is thought that a hydroxyl ion bridging the two metal ions takes part in nucleophilic attack on the phosphorusion.
Phosphatases can be subdivided based upon their substrate specificity.
Phosphatases act in opposition to
kinases/ phosphorylases, which add phosphate groups to proteins. The addition of a phosphate group may activate or de-activate an enzyme (e.g., Kinase signalling pathways [Seger & Krebs,The MAPK Signalling cascade, "FASEB J",9,pp726] ) or enable a protein-protein interaction to occur (e.g., SH3 domains [Ladbury, JE, Measurement of the formation of complexes in tyrosine kinase-mediated signal transduction,(2007), "Acta Cryst D",62,pp26] ); therefore phosphatases are integral to many signal transductionpathways. It should be noted that phosphate addition and removal do not necessarily correspond to enzyme activation or inhibition, and that several enzymes have separate phosphorylation sites for activating or inhibiting functional regulation. CDK, for example, can be either activated or deactivated depending on the specific amino acid residue being phosphorylated. Phosphates are important in signal transductionbecause they regulate the proteins to which they are attached. To reverse the regulatory effect, the phosphate is removed. This occurs on its own by hydrolysis, or is mediated by protein phosphatases.
erine/threonine-specific protein phosphatases
Serineand threoninephosphates are stable under physiological conditions, so a phosphatase has to remove the phosphate to reverse the regulation. There are several known groups with numerous members in each:
# PP1 (α, β, γ1, γ2)
# PP2 (formerly 2A)
# PP3 (formerly 2b, also known as
# PP5All but PP2C have
sequence homologyin the catalytic domain, but differ in substrate specifity.
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phosphatase — [ fɔsfataz ] n. f. • av. 1949; de phosphate et ase ♦ Biochim. Enzyme qui catalyse la libération d acide phosphorique à partir de ses esters organiques. ● phosphatase nom féminin Enzyme libérant de l acide phosphorique, présente dans de nombreux… … Encyclopédie Universelle
phosphatase — [fäs′fə tās΄] n. [< PHOSPHATE + ASE] any of various enzymes, found in body tissues and fluids, that hydrolyze phosphoric acid esters of organic compounds, liberating phosphate ions … English World dictionary
phosphatase — Any of a group of enzymes (EC 3.1.3.x) that liberate orthophosphate from phosphoric esters. SEE ALSO: phosphohydrolases. acid p. a p. with an optimum pH of less than 7.0 (for several isozymes, it is 5.4), notably present in the prostate gland;… … Medical dictionary
Phosphatase — Une phosphatase est une enzyme dont la fonction est d enlever un groupe phosphate d une molécule simple ou d une macromolécule biologique, par hydrolyse. En biotechnologie, elle peut agir sur l ADN et sur l ARN afin d empêcher leur… … Wikipédia en Français
Phosphatase — Phosphatasen Enzymklassifikationen EC, Kategorie … Deutsch Wikipedia
phosphatase — n. one of a group of enzymes capable of catalysing the hydrolysis of phosphoric acid esters. An example is glucose 6 phosphatase, which catalyses the hydrolysis of glucose 6 phosphate to glucose and phosphate. Phosphatases are important in the… … The new mediacal dictionary
phosphatase — noun Date: 1912 an enzyme that accelerates the hydrolysis and synthesis of organic esters of phosphoric acid and the transfer of phosphate groups to other compounds: a. alkaline phosphatase b. acid phosphatase … New Collegiate Dictionary
phosphatase — fosfatazė statusas T sritis chemija apibrėžtis Fermentas, katalizuojantis fosfatų atskėlimą. atitikmenys: angl. phosphatase rus. фосфатаза … Chemijos terminų aiškinamasis žodynas
phosphatase — (fos fah teīs ) An enzyme that catalyzes the hydrolytic removal of phosphate from molecules … Dictionary of microbiology
phosphatase — /fos feuh tays , tayz /, n. Biochem. any of several classes of esterases of varying specificity that catalyze the hydrolysis of phosphoric esters. [1910 15; PHOSPHATE + ASE] * * * … Universalium