Involved in the regulation of the intracellular balance of NAD and NADP, and is a key enzyme in the biosynthesis of NADP. Catalyzes specifically the phosphorylation on 2'-hydroxyl of the adenosine moiety of NAD to yield NADP. It can use ATP and other nucleoside triphosphates as a source of phosphorus. NADH cannot replace NAD as a substrate. ATP + NAD(+) = ADP + H(+) + NADP(+) Allosterically inhibited by NADPH and NADH. NADPH is the primary inhibitor during aerobic growth and NADH during anaerobic growth. Equilibrium mixture of dimer and tetramer. It is converted entirely to tetramer in the presence of the inhibitor NADPH. Belongs to the NAD kinase family.