Bisphosphate

Bisphosphate is a general term for any compound that bears two phosphate groups. The two phosphates may be bound as ester substituents on a single molecule, or the two phosphates may be directly linked to each other as a diphosphate (pyrophosphate) unit, in which case the linkage is P–O–P. The term thus covers a broad class of structures, from simple inorganic phosphate derivatives to organic molecules with two phosphate substituents.

In biochemistry, bisphosphate motifs occur in key metabolites and signaling molecules. A well-known example is fructose-1,6-bisphosphate, a central intermediate in glycolysis. Other biologically important examples include various inositol bisphosphates and other phosphorylated metabolites carrying two phosphate groups.

Chemically, bisphosphates are typically dianions at physiological pH. Bisphosphate esters are hydrolyzed by phosphatases, releasing inorganic phosphate and the attached alcohol or sugar moiety. Pyrophosphate-like bisphosphate units (two phosphates directly linked) are relatively high-energy and can contribute to the thermodynamics of enzymatic reactions; their hydrolysis is strongly exergonic and can help drive biosynthetic processes.

Nomenclature: The prefix bis- indicates two phosphate groups. The term is used broadly; when the two phosphates are directly bonded, the compound is usually called a diphosphate or pyrophosphate rather than a “bisphosphate,” while “bisphosphate” is common for molecules bearing two phosphate esters.

See also: Phosphate, Diphosphate, Pyrophosphate, Phosphatase.