The Chemical Biology of Phosphorus
Chapter 2: Inorganic Phosphate, Pyrophosphate, and Polyphosphate
Published:29 Oct 2020
Special Collection: 2020 ebook collectionSeries: Chemical Biology
The Chemical Biology of Phosphorus, The Royal Society of Chemistry, 2020, ch. 2, pp. 27-54.
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Given the pKa1 of H3PO4 (phosphoric acid) of 2.2 and pKa2 of 7.2, inorganic phosphate at physiological values of pH 7–7.4 is a mix of monoanions and dianions. In the PV oxidation state, the central phosphorus atom in inorganic phosphate and biological derivatives is electrophilic, capturable by cellular nucleophiles. Complementarily, the peripheral oxyanions can behave as nucleophiles, imparting bifunctional reactivity to PO42− ions. Most notable are phosphoric anhydrides, such as inorganic pyrophosphate, and inorganic triphosphate: kinetically stable but thermodynamically activated tetra-anionic and penta-anionic species in neutral aqueous solutions. These anionic kinetically stable anhydride linkages prefigure most of phosphorus chemical biology.