Adenylate kinase isoenzyme 6 (AK6) is a broad-specificity nucleoside monophosphate (NMP) kinase that catalyses the reversible transfer of the terminal phosphate group between nucleoside triphosphates and monophosphates []. AMP and dAMP are the preferred substrates, but CMP and dCMP are also good substrates. All nucleoside triphosphates ATP, GTP, UTP, CTP, dATP, dCTP, dGTP, and TTP are accepted as phosphate donors. It has also ATPase activity and may have a role in nuclear energy homeostasis. AK6 is involved in regulation of Cajal body (CB) formation [, ].This entry also includes related putative adenylate kinases from archaea.