ADP-Glucose (ADPG) is an immediate precursor used in the biosynthesis, by glucose addition, of storage polysaccharides in plants, green algae, and cyanobacteria, as well as structural polysaccharides in certain bacteria.[1],[2] It is used by amylose synthases or starch synthases in plastids in the production of amylose, amylopectins, starch, and other polysaccharides. ADPG is normally generated within plastids, although it can be biosynthesized in the cytoplasm of certain grasses and imported into plastids by a membrane-bound transporter.[3]
Cyclic ADP-ribose (cADP-ribose) is a calcium mobilizing nucleotide that is biosynthesized from NAD+ by cADP-ribose synthases, including CD38. cADP-Ribose appears to activate calcium channels in intracellular membranes, which in turn activate ryanodine receptors. 8-bromo-cADP-Ribose is a stable, cell-permeable analog that blocks calcium release evoked by cADP-ribose in sea urchin egg homogenates with an IC50 value of 1.7 μM. It is commonly used to investigate intracellular signaling through cADP-ribose in isolated cells and tissues.
NADP+ is the oxidized form of the electron donor nicotinamide adenine dinucleotide phosphate . It serves as a cofactor in various biological reactions. In addition, the balance between these reduced and oxidized forms plays key roles in diverse cellular functions, including cell survival, the maintenance of redox status, and intracellular signaling. For example, binding of NADP+ to β-subunits of Kv channels activates ion transport, whereas NADPH stabilizes channel inactivation. NADP+ is biosynthesized from NAD+ by NAD kinase, with ATP as the phosphoryl donor.