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In enzymology, a polyphosphate kinase , or polyphosphate polymerase, is an enzyme that catalyzes the formation of polyphosphate from ATP, with chain lengths of up to a thousand or more orthophosphate moieties.
Thus, the two substrates of this enzyme are ATP and polyphosphate n], whereas its two products are ADP and polyphosphate extended by one phosphate moiety n+1].
This enzyme is a membrane protein and goes through an intermediate stage during the reaction where it is autophosphorylated with a phosphate group covalently linked to a basic amino acyl residue through an N-P bond.
Several enzymes catalyze polyphosphate polymerization. Some of these enzymes couple phosphotransfer to transmembrane transport. These enzyme/transporters are categorized in the Transporter Classification Database under the Polyphosphate Polymerase/YidH Superfamily and are transferases that transfer phosphoyl groups with polyphosphate as the acceptor. The systematic name of this enzyme class is ATP:polyphosphate phosphotransferase. This enzyme is also called polyphosphoric acid kinase.