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 well as inorganic polyphosphate (poly(P)) as a source of phosphorus. ATP + NAD(+) = ADP + H(+) + NADP(+) Allosterically inhibited by NADP, NADPH, and NADH, at concentrations lower than 0.5 mM. Completely inhibited by p-chloromercuribenzoate. Optimum pH is 6.5 in sodium-acetate at 50 degrees Celsius for poly(P)-dependent kinase activity and optimum pH is 8 in Tris-HCl at 50 degrees Celsius for ATP-dependent kinase activity. Optimum temperature is 50 degrees Celsius. Homotetramer. Was identified as a high-confidence drug target. Belongs to the NAD kinase family.