phosphomonoester

Phosphomonoester is an ester of phosphoric acid with a single organic substituent. It is formed when one hydroxyl group of phosphoric acid is replaced by an alkyl or aryl group, giving a structure broadly described as RO-PO(=O)(OH)2. This class is distinct from phosphodiesters (two ester-linked substituents) and phosphotriesters (three).

Biological examples include sugar phosphates such as glucose-6-phosphate and fructose-6-phosphate, as well as nucleotide monophosphates in which the sugar is linked to a single phosphate via a phosphomonoester bond. Phosphomonoesters are typically highly hydrophilic and carry a negative charge at physiological pH.

Formation and turnover: In cells, phosphomonoesters are formed by kinases transferring a phosphate from ATP to an alcohol-bearing substrate, or by chemical esterification. They are hydrolyzed by phosphatases (acid and alkaline phosphatases) to yield the corresponding alcohol and inorganic phosphate. Phosphorylation of proteins, yielding phosphomonoester bonds on serine, threonine, or tyrosine residues, is a major mechanism of metabolic regulation and signal transduction.

Industrial and laboratory contexts: They are used as substrates in phosphatase assays (such as p-nitrophenyl phosphate) and as intermediates in nucleotide and carbohydrate metabolism studies. In biochemistry, the term phosphomonoester is often used to describe a single phosphate ester group within larger molecules.