Figure 1

Schematic representation of the structure and enzymatic activity of CD38. CD38 converts the substrate NAD⁺ into cyclic ADP ribose and NAADP⁺; it can also act on its own product, cADPR, to form the linear molecule ADP-ribose. Independently of its enzymatic activity, CD38 can trigger intracellular signaling cascades that mobilize intracellular calcium stores.