Figure 1.

NAD kinase reactions. (A) ATP-NAD kinase reaction. NAD⁺ is phosphorylated to NADP⁺ by using only ATP. (B) ATP/poly(P)-NAD kinase reaction. NAD⁺ is phosphorylated to NADP⁺ by using ATP or poly(P). Linear and cyclic poly(P)s are then utilized. (C) Structures of NAD⁺ and NADH. A hydride ion (H⁻) is added to a nicotinamide moiety of NAD⁺, resulting in NADH. This figure was reproduced from S. Kawai and K. Murata (2008) Biosci. Biotechnol. Biochem. 72, 919–930 (Ref. 63) with some modifications.