NAD kinase catalyzes the transfer of a phosphate group from ATP to NAD+ to generate NADP+, which in its reduced form acts as an electron donor for biosynthetic reactions. NADP+ is an essential coenzyme in metabolism and provides reducing power to biosynthetic processes such as fatty acid biosynthesis. NAD kinase from Bacillus subtilis is not ATP-dependent but has a broader substrate specificity than human NAD kinase. It can economically produce NADP+ by using other nucleoside triphosphates as well as inorganic polyphosphate as a source of phosphorus. Catalytic activity: ATP + NAD+ = ADP + NADP+