Pyrophosphate

In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P-O-P linkage. A number of pyrophosphate salts exist, such as Na2H2P2O7. Often pyrophosphates are called diphosphates. The parent pyrophosphates are derived from partial or complete neutralization of pyrophosphoric acid. Important salts include disodium pyrophosphate and tetrasodium pyrophosphate. The pyrophosphate bond, as found in ATP, is very important in biochemistry. In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P-O-P linkage. A number of pyrophosphate salts exist, such as Na2H2P2O7. Often pyrophosphates are called diphosphates. The parent pyrophosphates are derived from partial or complete neutralization of pyrophosphoric acid. Important salts include disodium pyrophosphate and tetrasodium pyrophosphate. The pyrophosphate bond, as found in ATP, is very important in biochemistry. Pyrophosphates are prepared by heating phosphates, hence the name pyro-phosphate (from the Ancient Greek: πῦρ, πυρός, romanized: pyro, lit. 'fire'). More precisely, they are generated by heating phosphoric acids to the extent that a condensation reaction occurs. Pyrophosphates are generally white or colorless. The alkali metal salts are water soluble. They are good complexing agents for metal ions (such as calcium and many transition metals) 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 anion P2O4−7 is abbreviated PPi, standing for inorganic pyrophosphate. It is formed by the hydrolysis of ATP into AMP in cells. 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 in which pyrophosphate reacts with the 3′-nucleosidemonophosphate (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 P2O4−7, and is an acid anhydride of phosphate. It is unstable in aqueous solution and hydrolyzes into inorganic phosphate: