CD38 and prostate cancer: Interestingly, the carboxyl-terminal catalytic domain of CD38 media has two opposing orientations and is therefore able to mobilize either intra- or extracellular NAD+ pools.300 However, CD38 expression specifically leads to the consumption of extracellular NAD+ and not intracellular NAD+ in prostate cancer cells.23 Moreover, CD38 also consumes extracellular NMN, generating NAM, which can be converted to NAD+ through NAMPT and NMNAT after crossing the plasma membrane.123 Another important membrane-bound enzyme that degrades extracellular NAD+ is CD73.