NME4 is a member of the NDK family. NME4 are ubiquitous enzymes which catalyze transfer of gamma-phosphates, using a phosphohistidine intermediate, between nucleoside and dioxynucleoside tri- and diphosphates. The enzymes are products of the nm23 gene family that include NME4. NME4 has a key part in the synthesis of nucleoside triphosphates other than ATP.