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Encyclopedia > Phosphatase

A phosphatase is an enzyme that dephosphorylates its substrate; i.e., it hydrolyses phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group. 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. Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... A phosphorylated serine residue Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule or the introduction of a phosphate group into an organic molecule. ... Look up substrate in Wiktionary, the free dictionary. ... Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. ... Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is an inorganic mineral acid having the chemical formula H3PO4. ... A carboxylic acid ester. ... Above is a ball-and-stick model of the inorganic hydrogenphosphate anion (HPO42−). Colour coding: P (orange); O (red); H (white). ... An electrostatic potential map of the nitrate ion (NO3−). Areas coloured red are lower in energy than areas colored yellow An ion is an atom or group of atoms which have lost or gained one or more electrons, making them negatively or positively charged. ... // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... Phosphorylase is an enzyme that catalyzes the production of glucose phosphate from glycogen and inorganic phosphate. ... In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific target molecules (substrates); the process is termed phosphorylation. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Ball and stick model of alkaline phosphatase Alkaline phosphatase (ALP) (EC 3. ...


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). Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ...

Contents

Mechanism

CDPs catalyse the hydrolysis of a phosphoester bond via a phospho-cysteine intermediate [1].

Mechanism of Tyrosine dephosphorylation by a CDP

The free cysteine nucleophile forms a bond with the phosphorus atom 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 acid residue (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. Image File history File links Size of this preview: 516 × 600 pixelsFull resolution (1266 × 1472 pixel, file size: 105 KB, MIME type: image/png) Made by me, adapted from published work. ... Image File history File links Size of this preview: 516 × 600 pixelsFull resolution (1266 × 1472 pixel, file size: 105 KB, MIME type: image/png) Made by me, adapted from published work. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... General Name, Symbol, Number phosphorus, P, 15 Chemical series nonmetals Group, Period, Block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ... Phenylalanine is one of the standard amino acids. ...


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 phosphorus ion. General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Standard atomic weight 54. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Standard atomic weight 65. ... In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... General Name, Symbol, Number phosphorus, P, 15 Chemical series nonmetals Group, Period, Block 15, 3, p Appearance waxy white/ red/ black/ colorless Standard atomic weight 30. ...


Sub-types

Phosphatases can be subdivided based upon their substrate specificity.

Class Example Substrate Reference
Tyrosine-specific phosphatases PTP1B Phospho-Tyrosine [2]
Serine/Threonine specific phosphatases PP2C Phospho-Serine/Threonine [3]
Dual Specificity Phosphatases VHR Phospho-Tyrosine/Serine/Threonine [4]
Histidine Phosphatase PHP Phospho-Histidine [5]
Lipid Phosphatase PTEN Phosphatidyl-Inositol-3,4,5-Triphosphate [6]

Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells to synthesize proteins. ... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Threonine is one of the 20 natural amino acids. ... Histidine is one of the 20 most common natural amino acids present in proteins. ...

Physiological Relevance

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[7] ) or enable a protein-protein interaction to occur (e.g., SH3 domains [8]); therefore phosphatases are integral to many signal transduction pathways. 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 transduction because 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. In biochemistry, a kinase is a type of enzyme that transfers phosphate groups from, for example, ATP to a specified substrate or target; the process is termed phosphorylation. Typically, the target is activated or energized by being phosphorylated. ... Phosphorylase is a family of allosteric enzymes that catalyze the production of glucose-1-phosphate from a polyglucose such as glycogen, starch or maltodextrin. ... Overview of signal transduction pathways In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in... Cyclin-dependent kinase is a protein kinase involved in regulation of the cell cycle. ... Above is a ball-and-stick model of the inorganic hydrogenphosphate anion (HPO42−). Colour coding: P (orange); O (red); H (white). ... Overview of signal transduction pathways In biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another, most often involving ordered sequences of biochemical reactions inside the cell, that are carried out by enzymes and linked through second messengers resulting in... Hydrolysis is a chemical reaction or process in which a chemical compound reacts with water. ...


Protein Phosphatases

Serine/threonine-specific protein phosphatases

Serine and threonine phosphates are stable under physiological conditions, so a phosphatase has to remove the phosphate to reverse the regulation. There are four known groups: Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Threonine is one of the 20 natural amino acids. ...

  1. PP1 (α, β, γ1, γ2)
  2. PP2A
  3. PP2B (AKA calcineurin)
  4. PP2C
  5. PP4
  6. PP5

The first three have sequence homology in the catalytic domain, but differ in substrate specifity. Calcineurin (CN) is a protein phosphatase also known as protein phosphatase 2B (PP2B). ... Two or more structures are said to be homologous if they are alike because of shared ancestry, such as two chromosomes that contain the same genes. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Within a protein, a structural domain (domain) is an element of overall structure that is self-stabilizing and often folds independently of the rest of the protein chain. ...


Ser/Thr-specific protein phosphatases are regulated by their location within the cell and by specific inhibitor proteins. Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... HIV protease in a complex with the protease inhibitor ritonavir. ...


See also

Acid salts are a class of chemical compounds that are formed when a dibasic or tribasic acid has been neutralized to some degree. ...

References

  1. ^ Barford, D. Molecular mechanisms of the protein serine/threonine phosphatases, (1996) Trends Bioch Sci,21, 11, pp407
  2. ^ Zhong-Yin Zhang, PROTEIN TYROSINE PHOSPHATASES: Structure and Function, Substrate Specificity, and Inhibitor Development (2002), Annual Review of Pharmacology and Toxicology,42, pp209
  3. ^ Mumby, MC & Walter, G. Protein Serine/Threonine Phosphatases: Structure, Regulation, and Functions in Cell Growth (1993) Physiological Reviews,73,pp673
  4. ^ Camps, S et al, Dual specificity phosphatases: a gene family for control of MAP kinase function. (2000) FASEB J,1,pp16
  5. ^ Baumner, H et al, Expression of Protein Histidine Phosphatase in Escherichia coli, Purification, and Determination of Enzyme Activity. (2006), Methods Mol Biol, 365, pp247
  6. ^ Maehama, T. et al, The tumour suppressor PTEN: involvement of a tumour suppressor candidate protein in PTEN turnover (2004) Biochem. Soc. Trans. 32, pp343
  7. ^ Seger & Krebs,The MAPK Signalling cascade, FASEB J,9,pp726
  8. ^ Ladbury, JE, Measurement of the formation of complexes in tyrosine kinase-mediated signal transduction,(2007), Acta Cryst D,62,pp26

External links


  Results from FactBites:
 
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Phosphatase - Wikipedia, the free encyclopedia (220 words)
A phosphatase is an enzyme that hydrolyses phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group.
A common phosphatase in the body is alkaline phosphatase.
However, the metalloenzymes by far comprise the greatest bulk of phosphatases, and contain such enzymes as alkaline phosphatase (three metal ions, only two of which are catalytically active), the serine threonine phosphatases and inositol monophosphatase (a key enzyme in manic depression).
  More results at FactBites »

 
 

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