REGULATION OF NAD(-DEPENDENT AUTO-ADP-RIBOSYLATION() GLYCOHYDROLASE ACTIVITY BY NAD(+))

NAD(+) glycohydrolase (NADase; EC 3.2.2.5) is an enzyme that catalyses hydrolysis of NAD(+) to produce ADP-ribose and nicotinamide. Its phys iological role and the regulation of its enzymic activity have not bee n fully elucidated. In the present study, the mechanism of self-inacti vation of NADase by its substrate, NAD+, was investigated by using int act rabbit erythrocytes and purified NADase. Our results suggest that inactivation of NADase was due an auto-ADP-ribosylation reaction. ADP- ribosylated NADase of rabbit erythrocytes was deADP-ribosylated when i ncubated without NAD(+), and thus enzyme activity was simultaneously r estored. These findings suggest that reversible auto-ADP-ribosylation of NADase might regulate the enzyme's activity in vivo.