Inorganic polyphosphate kinase and adenylate kinase participate in the polyphosphate : AMP phosphotransferase activity of Escherichia coli

Polyphosphate kinase (PPK), responsible for the processive synthesis of ino rganic polyphosphate (polyP) from ATP in Escherichia coli, can transfer in reverse the terminal phosphate residue of polyp to ADP to yield ATP. PolyP also serves as a donor in a polyP:AMP phosphotransferase (PAP) activity obs erved in extracts of Acinetobacter johnsonii and Myxococcus xanthus. We hav e found that overexpression of the gene encoding PPK results in a large enh ancement of PAP activity in E. coli. The PAP activity requires both PPK and adenylate kinase in equimolar amounts. PPK and adenylate kinase form a com plex in the presence of polyphosphate. We discuss a phosphotransfer mechani sm that involves both enzymes and enables polyp to be a phospho-donor to AM P.