Sirtuin - Wikipedia, the free encyclopedia

Sirtuin - Wikipedia, the free encyclopedia: "Silent Information Regulator Two (Sir2) proteins, or sirtuins"

Silent Information Regulator Two (Sir2) proteins, or sirtuins, are a class of proteins that possess either histone deacetylase or mono-ribosyltransferase activity and are found in organisms ranging from bacteria to humans.[2][3] Named after the yeast silent mating-type information regulation two,[4] the gene responsible for cellular regulation in yeast, sirtuins regulate important biological pathways in eubacteria, archaea and eukaryotes.




Yeast Sir2 and some, but not all, sirtuins are protein deacetylases. Unlike other known protein deacetylases, which simply hydrolyze acetyl-lysine residues, the sirtuin-mediated deacetylation reaction couples lysine deacetylation to NAD hydrolysis. This hydrolysis yields O-acetyl-ADP-ribose, the deacetylated substrate and nicotinamide, itself an inhibitor of sirtuin activity. The dependence of sirtuins on NAD links their enzymatic activity directly to the energy status of the cell via the cellular NAD:NADH ratio, the absolute levels of NAD, NADH or nicotinamide or a combination of these variables