Involved in the regulation of the intracellular balance between NAD(H) and NADP(H), and is a key enzyme in the biosynthesis of NADP. Catalyzes the phosphorylation and dephosphorylation of NAD and NADP, respectively. Although it shows conflicting dual activities and is able to supply NADP, it seems that its physiological role is to prevent excess accumulation of NADP. Kinase can use ATP and other nucleoside triphosphates (UTP, TTP, CTP, GTP) as well as inorganic polyphosphate (poly(P)) as phosphoryl donors, however poly(P) is not considered to be the physiological phosphoryl donor. NAD is the preferred substrate for the kinase, but NADH can also be used as phosphoryl acceptor. Phosphatase can use NADP or NADPH as phosphoryl donor, but NADP is the preferred substrate. Phosphatase also has an activity toward the terminal phosphate group at C-2 of adenosine in 2'-AMP and toward the phosphate group at C-1 of fructose 1,6-bisphosphate, but not toward inositol 1-phosphate. ATP + NAD(+) = ADP + H(+) + NADP(+) H2O + NADP(+) = NAD(+) + phosphate Mg(2+). NAD and pNPPase kinase show maximum activities at 50 and 20 mM magnesium, respectively. Phosphatase activity is slightly inhibited by ADP, NADPH and ATP, and moderately inhibited by NAD and 5'-AMP. Kinase activity is slightly inhibited by ADP and NADP. kcat is 399 sec(-1) for kinase activity with ATP as substrate. kcat is 424 sec(-1) for kinase activity with NAD as substrate. kcat is 906 sec(-1) for phosphatase activity with fructose 1,6-bisphosphate and NADP as substrates. kcat is 1007 sec(-1) for phosphatase activity with NADPH as substrate. Optimum temperature is 100 degrees Celsius for phosphatase and kinase activities. Both are inactive below 60 degrees Celsius. Homotetramer. The phosphatase is inert toward the substrates of NAD kinase (NAD, NADH, ATP, and poly(P)). This demonstrates that the phosphatase activity never interferes with the NAD kinase activity by degrading its substrates (PubMed:16192277). In the N-terminal section; belongs to the inositol monophosphatase superfamily. In the C-terminal section; belongs to the NAD kinase family.