Phosphoryl transfer is the name given to the chemical process of the transfer of the phosphoryl group (PO3) from a phosphate ester or anhydride to a nucleophile. Nucleophilic attack by water on a phosphate monoester gives the hydrolysis product inorganic phosphate. This net dephosphorylation reaction is the process catalysed by phosphatases. The formation of phosphate esters is termed phosphorylation, and is accomplished in biological systems by kinases.