Pyrophosphate: Difference between revisions
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The pyrophosphate anion has the structure P<sub>2</sub>O<sub>7</sub><sup>4−</sup>, and is an [[acid]] [[anhydride]] of [[phosphate]]. It is unstable in [[aqueous solution]] and in the absence of enzymic catalysis [[hydrolysis|hydrolyze]]s extremely slowly into inorganic phosphate in all but highly acidic media:<ref name=Huebner>{{ cite journal |author=Huebner PWA, Milburn RM |title=Hydrolysis of pyrophosphate to orthophosphate promoted by cobalt(III). Evidence for the role of polynuclear species |journal=Inorg Chem. |year=1980 |volume=19 |issue=5 |pages=1267-72 |month=May |pmid= |doi=10.1021/ic50207a032 }}</ref> | The pyrophosphate anion has the structure P<sub>2</sub>O<sub>7</sub><sup>4−</sup>, and is an [[acid]] [[anhydride]] of [[phosphate]]. It is unstable in [[aqueous solution]] and in the absence of enzymic catalysis [[hydrolysis|hydrolyze]]s extremely slowly into inorganic phosphate in all but highly acidic media:<ref name=Huebner>{{ cite journal |author=Huebner PWA, Milburn RM |title=Hydrolysis of pyrophosphate to orthophosphate promoted by cobalt(III). Evidence for the role of polynuclear species |journal=Inorg Chem. |year=1980 |volume=19 |issue=5 |pages=1267-72 |month=May |pmid= |doi=10.1021/ic50207a032 }}</ref> | ||
* P<sub>2</sub>O<sub>7</sub><sup>4−</sup> + H<sub>2</sub>O | * P<sub>2</sub>O<sub>7</sub><sup>4−</sup> + H<sub>2</sub>O → 2 HPO<sub>4</sub><sup>2−</sup> | ||
or in shorthand notation: | or in shorthand notation: | ||
* PP<sub>i</sub> + H<sub>2</sub>O | * PP<sub>i</sub> + H<sub>2</sub>O → 2 P<sub>i</sub> | ||
Enzyme EC 3.6.1.1 catalyzes this hydrolysis.<ref name=3.6.1.1>{{ cite web |title=NiceZyme View of ENZYME: EC 3.6.1.1 |url=http://www.expasy.org/enzyme/3.6.1.1 }}</ref> Specificity varies with the source and with the activating metal ion, e.g. Mg<sup>2+</sup>.<ref name=3.6.1.1/> | Enzyme EC 3.6.1.1 catalyzes this hydrolysis.<ref name=3.6.1.1>{{ cite web |title=NiceZyme View of ENZYME: EC 3.6.1.1 |url=http://www.expasy.org/enzyme/3.6.1.1 }}</ref> Specificity varies with the source and with the activating metal ion, e.g. Mg<sup>2+</sup>.<ref name=3.6.1.1/> | ||
This hydrolysis to inorganic phosphate effectively renders the cleavage of ATP to AMP and PP<sub>i</sub> ultimately [[hydrolysis|irreversible]], and biochemical reactions coupled to this hydrolysis are irreversible as well. | This hydrolysis to inorganic phosphate effectively renders the cleavage of ATP to AMP and PP<sub>i</sub> ultimately [[hydrolysis|irreversible]], and biochemical reactions coupled to this hydrolysis are irreversible as well, unless EC 3.6.1.1 is present. EC 3.6.1.1 can reverse the hydrolysis.<ref name=3.6.1.1/> | ||
From the standpoint of [[high energy phosphate]] accounting, the hydrolysis of ATP to AMP and PP<sub>i</sub> will require two high energy phosphates, as to reconstitute AMP into ATP will require two phosphorylation reactions. | From the standpoint of [[high energy phosphate]] accounting, the hydrolysis of ATP to AMP and PP<sub>i</sub> will require two high energy phosphates, as to reconstitute AMP into ATP will require two phosphorylation reactions. | ||
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Editor-In-Chief: Henry A. Hoff
In chemistry, the anion, the salts, and the esters of pyrophosphoric acid are called pyrophosphates. The anion P2O74− is abbreviated PPi and is formed by the hydrolysis of ATP into AMP in cells.
- ATP → AMP + PPi
For example, when a nucleotide is incorporated into a growing DNA or RNA strand by a polymerase, pyrophosphate (PPi) is released. Pyrophosphorolysis is the reverse of the polymerization reaction where 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 in the absence of enzymic catalysis hydrolyzes extremely slowly into inorganic phosphate in all but highly acidic media:[1]
- P2O74− + H2O → 2 HPO42−
or in shorthand notation:
- PPi + H2O → 2 Pi
Enzyme EC 3.6.1.1 catalyzes this hydrolysis.[2] Specificity varies with the source and with the activating metal ion, e.g. Mg2+.[2]
This hydrolysis to inorganic phosphate effectively renders the cleavage of ATP to AMP and PPi ultimately irreversible, and biochemical reactions coupled to this hydrolysis are irreversible as well, unless EC 3.6.1.1 is present. EC 3.6.1.1 can reverse the hydrolysis.[2]
From the standpoint of high energy phosphate accounting, the hydrolysis of ATP to AMP and PPi will require two high energy phosphates, as to reconstitute AMP into ATP will require two phosphorylation reactions.
- AMP + ATP → 2 ADP
- 2 ADP + 2 Pi → 2 ATP
The synthesis of tetraethyl pyrophosphate was first described in 1854 by Philip de Clermount at a meeting of the French Academy of Sciences.
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.
References
- ↑ Huebner PWA, Milburn RM (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. Unknown parameter
|month=ignored (help) - ↑ 2.0 2.1 2.2 "NiceZyme View of ENZYME: EC 3.6.1.1".
See also
External links
- Pyrophosphates at the US National Library of Medicine Medical Subject Headings (MeSH)