Broad-specificity nucleoside monophosphate (NMP) kinase that catalyzes the reversible transfer of the terminal phosphate group between nucleoside triphosphates and monophosphates. AMP is the best phosphate acceptor, and CMP is also a good substrate. All nucleoside triphosphates ATP, TTP, CTP, GTP, and UTP are accepted as phosphate donors. ATP is the best phosphate donor. May have a role in nuclear energy homeostasis. AMP + ATP = 2 ADP Monomer and homodimer. Belongs to the adenylate kinase family. AK6 subfamily.