Figure 1.

NAD⁺ salvage pathway and NAD⁺-dependent enzymatic reactions. NAD⁺ salvage pathway (top) NAM or NR are converted to NMN by NAMPT or NMRK, respectively. NMNAT generates NAD⁺ from NMN. NAD⁺ can be reversibly reduced and oxidized or utilized by NADases (SIRTs, PARPs, CD38, and SARM1), which produce NAM as a byproduct that can be re-used to form NAD⁺. NADase reactions (bottom). PARPs add ADPR to substrates. SIRTs remove acetyl groups from target substrates. CD38 and SARM1 generate ADPR/cADPR, which are important for second messenger signaling pathways. All figures were generated using BioRender.com.