Figure 1: Schematic representation of the enzyme-catalyzed reversible mono-ADP-ribosylation reaction. The diagram shows the enzymatic transfer of the ADP-ribose portion from NAD to the guanidine group of an arginine target. Nicotinamide, the remaining portion of NAD, is simultaneously released. The native arginine is restored by the reaction catalyzed by an ADP-ribosylarginine hydrolase that cleaves the 𝛼 - glycosidic bond with the release of ADP-ribose.