Autophosphorylation of nucleoside diphosphate kinase on non-histidine residues.

Recently, several reports appeared which described auto-phosphorylation of NDP kinase on residues different from the active-site histidine. Based on these findings conclusions were drawn with respect to a regulation of enzyme activity and to a possible role as a metastasis suppressor. In this paper we show that although non-histidine autophosphorylation occurs on NDP kinases from mammals, lower eukaryotes and bacteria, less than 0.2% of the subunits are phosphorylated. Using site-directed mutagenesis, we show that the active site histidine is essential for non-histidine autophosphorylation. The low stoichiometry of phosphate incorporation excludes a role of autophosphorylation in regulating overall enzyme activity.