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. Author manuscript; available in PMC: 2018 Apr 1.
Published in final edited form as: Trends Mol Med. 2017 Mar 10;23(4):320–331. doi: 10.1016/j.molmed.2017.02.005

Figure 1. Mitochondrial Sirtuins Are NAD+-Dependent Deacylases and ADP-Ribosyl Transferases.

Figure 1

A. mitochondrial sirtuins remove acyl moieties by positioning NAD+ to nucleophilically attack the acylated lysine. As a result, NAD+ is cleaved and 2′-O-acyl-ADP ribose and nicotinamide are formed in the process. The best characterized acyl modifications removed by mitochondrial sirtuins are shown in the inset. B. SIRT4 catalyzes the transfer of ADP-ribose from NAD+ to arginine, cysteine, serine and threonine substrates. Here, NAD+ is used by SIRT4 to nucleophilically attack the substrate yielding nicotinamide as a byproduct.