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An enzyme that catalyzes the transfer of the ADP-ribose moiety from NAD to specific protein substrates with agmatine, arginine-type compounds, or guanidine as acceptors. This reaction can be catalyzed by prokaryotic and eukaryotic enzyme systems. Mono-ADP-ribosylation is a mechanism of action common to several bacterial toxins. It effects profound changes in cellular metabolism, such as activation of adenylate cyclase, regulation of protein synthesis at the level of elongation factor 2, and ion transport across biological membranes. EC 2.4.2.31.