AUTOPHOSPHORYLATION OF NUCLEOSIDE DIPHOSPHATE KINASE ON NON-HISTIDINERESIDUES

Recently, several reports appeared which described auto-phosphorylatio n of NDP kinase on residues different from the active-site histidine. Based on these findings conclusions were drawn with respect to a regul ation of enzyme activity and to a possible role as a metastasis suppre ssor. In this paper we show that although non-histidine autophosphoryl ation occurs on NDP kinases from mammals, lower eukaryotes and bacteri a, less than 0.2% of the subunits are phosphorylated. Using site-direc ted mutagenesis, we show that the active site histidine is essential f or non-histidine autophosphorylation. The low stoichiometry of phospha te incorporation excludes a role of autophosphorylation in regulating overall enzyme activity.