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. Author manuscript; available in PMC: 2012 Jun 4.
Published in final edited form as: Exp Gerontol. 2006 Jul 13;41(8):718–726. doi: 10.1016/j.exger.2006.06.003

Fig. 1.

Fig. 1

The sirtuin/class III HDAC deacetylation reaction and regulation by nicotinamide. Step 1 is a reversible base-exchange reaction in which a peptidyl intermediate is formed between the acetyl group on the lysine of the polypeptide to generate 1′-O-α-peptidylamidate-ADP-ribose, with the release of nicotinamide (NAM). Step two is the deacetylation of the lysine by hydrolytic attack. The peptidyl intermediate is sufficiently stable to permit regeneration of NAD+ in the presence of elevated nicotinamide concentrations. Figure adapted from Bitterman et al. (2002).