Self‐aggregation of purified and membrane‐bound erythrocyte CD38 induces extensive decrease of its ADP‐ribosyl cyclase activity

The transmembrane glycoprotein CD38 is a bifunctional enzyme that catalyzes at its ectocellular domain both the synthesis and the hydrolysis of cyclic ADP-ribose (cADPR). The complete reaction, converting NAD+ to nicotinamide and ADP-ribose, reproduces an NAD+glycohydrolase (NADase) reaction. CD38 purified from human erythrocyte membranes has been recently shown to undergo stable oligomerization induced by either NAD+ or beta-mercaptoethanol. We demonstrate that oligomerization is also triggered by reduced glutathione (GSH) and that the GSH-induced self-aggregation of purified CD38 is accompanied by extensive and comparable decrease of its ADP-ribosyl cyclase and NADase activities. GSH-induced oligomerization of CD38 and strong enzyme inactivation take place also in situ on erythrocyte membranes.