definição e significado de Pyrophosphate

Pyrophosphate


Other names Diphosphate
Identifiers
PubChem	644102
ChemSpider	559142^Y
DrugBank	DB04160
ChEBI	CHEBI:18361^Y
Jmol-3D images	Image 1
SMILES [O-]P(=O)([O-])OP(=O)([O-])[O-]
InChI InChI=1S/H4O7P2/c1-8(2,3)7-9(4,5)6/h(H2,1,2,3)(H2,4,5,6)/p-4^Y Key: XPPKVPWEQAFLFU-UHFFFAOYSA-J^Y InChI=1/H4O7P2/c1-8(2,3)7-9(4,5)6/h(H2,1,2,3)(H2,4,5,6)/p-4 Key: XPPKVPWEQAFLFU-XBHQNQODAI
Properties
Molecular formula	P₂O₇⁴⁻
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

In chemistry, the anion, the salts, and the esters of pyrophosphoric acid are called pyrophosphates. Any salt or ester containing two phosphate groups is called a diphosphate. As a food additive, diphosphates are known as E450.

1 Chemistry
2 In biochemistry
3 See also
4 References
5 Further reading
6 External links

Chemistry

Pyrophosphates were originally prepared by heating phosphates (pyro from the Greek, meaning "fire"). Pyrophosphates generally exhibit the highest solubilities among the phosphates;^[1] moreover, they are good complexing agents and have many uses in industrial chemistry. Pyrophosphate is the first member of an entire series of polyphosphates.

The term pyrophosphate is also the name of esters formed by the condensation of a phosphorylated biological compound with inorganic phosphate as for dimethylallyl pyrophosphate. This bond is also referred to as a high-energy phosphate bond.

The synthesis of tetraethyl pyrophosphate was first described in 1854 by Philip de Clermount at a meeting of the French Academy of Sciences.

In biochemistry

Main article: Biochemistry

Pyrophosphates are very important in biochemistry. The anion P₂O₇⁴⁻ is abbreviated PP_i and is formed by the hydrolysis of ATP into AMP in cells.

ATP → AMP + PP_i

For example, when a nucleotide is incorporated into a growing DNA or RNA strand by a polymerase, pyrophosphate (PP_i) is released. Pyrophosphorolysis is the reverse of the polymerization reaction in which pyrophosphate reacts with the 3'-nucleotidemonophosphate (NMP or dNMP), which is removed from the oligonucleotide to release the corresponding triphosphate (dNTP from DNA, or NTP from RNA).

The pyrophosphate anion has the structure P₂O₇⁴⁻, and is an acid anhydride of phosphate. It is unstable in aqueous solution and hydrolyzes into inorganic phosphate:

P₂O₇⁴⁻ + H₂O → 2 HPO₄²⁻

or in biologists' shorthand notation:

PP_i + H₂O → 2 P_i

In the absence of enzymic catalysis, hydrolysis reactions of simple polyphosphates such as pyrophosphate, linear triphosphate, ADP, and ATP normally proceed extremely slowly in all but highly acidic media.^[2]

(The reverse of this reaction is a method of preparing pyrophosphates by heating phosphates.)

This hydrolysis to inorganic phosphate effectively renders the cleavage of ATP to AMP and PP_i irreversible, and biochemical reactions coupled to this hydrolysis are irreversible as well.

PP_i occurs in synovial fluid, blood plasma, and urine at levels sufficient to block calcification and may be a natural inhibitor of hydroxyapatite formation in extracellular fluid (ECF).^[3] Cells may channel intracellular PP_i into ECF.^[4] ANK is a nonenzymatic plasma-membrane PP_i channel that supports extracellular PP_i levels.^[4] Defective function of the membrane PP_i channel ANK is associated with low extracellular PP_i and elevated intracellular PP_i.^[3] Ectonucleotide pyrophosphatase/phosphodiesterase (ENPP) may function to raise extracellular PP_i.^[4]

From the standpoint of high energy phosphate accounting, the hydrolysis of ATP to AMP and PP_i requires two high-energy phosphates, as to reconstitute AMP into ATP requires two phosphorylation reactions.

AMP + ATP → 2 ADP

2 ADP + 2 P_i → 2 ATP

References

^ C.Michael Hogan. 2011. Phosphate. Encyclopedia of Earth. Topic ed. Andy Jorgensen. Ed.-in-Chief C.J.Cleveland. National Council for Science and the Environment. Washington DC
^ Huebner PWA, Milburn RM (May 1980). "Hydrolysis of pyrophosphate to orthophosphate promoted by cobalt(III). Evidence for the role of polynuclear species". Inorg Chem. 19 (5): 1267–72. DOI:10.1021/ic50207a032.
^ ^a ^b Ho AM, Johnson MD, Kingsley DM (Jul 2000). "Role of the mouse ank gene in control of tissue calcification and arthritis". Science. 289 (5477): 265–70. DOI:10.1126/science.289.5477.265. PMID 10894769.
^ ^a ^b ^c Rutsch F, Vaingankar S, Johnson K, Goldfine I, Maddux B, Schauerte P, Kalhoff H, Sano K, Boisvert WA, Superti-Furga A, Terkeltaub R (Feb 2001). "PC-1 nucleoside triphosphate pyrophosphohydrolase deficiency in idiopathic infantile arterial calcification". Am J Pathol. 158 (2): 543–54. DOI:10.1016/S0002-9440(10)63996-X. PMC 1850320. PMID 11159191. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1850320.

External links

Look up diphosphate or pyrophosphate in Wiktionary, the free dictionary.

Pyrophosphates at the US National Library of Medicine Medical Subject Headings (MeSH)

Phosphorus compounds

PBr₃ PBr₅ PCl₃ PCl₅ PF₃ PF₅ PH₃ PI₃ P₂O₃ P₂O₅ P₄S₃ P₄S₁₀

Definição e significado de Pyrophosphate

Definição

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Dicionario analógico

Pyrophosphate

Contents

Chemistry

In biochemistry

See also

References

Further reading

External links