Members of this family are NAD kinases . The enzymes catalyse the phosphorylation of NAD to NADP utilizing ATP and other nucleoside triphosphates, as well as inorganic polyphosphate, as a source of phosphorus. Such enzymes are thus designated poly(P)/ATP-NAD kinases []. NAD kinase is one of the key enzymes regulating the cellular NADP(H) level, and therefore NADPH-dependent reductive biosynthetic pathways [].