Propofol Inhibits SIRT2 Deacetylase Through a Conformation-Specific, Allosteric Site [Enzymology]

February 9th, 2015 by Weiser, B. P., Eckenhoff, R. G.

Meta-azi-propofol (AziPm) is a photoactive analog of the general anesthetic propofol. We photolabeled a myelin-enriched fraction from rat brain with [3H]AziPm and identified the sirtuin deacetylase SIRT2 as a target of the anesthetic. AziPm photolabeled three SIRT2 residues (Tyr139, Phe190, and Met206) that are located in a single allosteric protein site, and propofol inhibited [3H]AziPm photolabeling of this site in myelin SIRT2. Structural modeling and in vitro experiments with recombinant human SIRT2 determined that propofol and [3H]AziPm only bind specifically and competitively to the enzyme when co-equilibrated with other substrates, which suggests that the anesthetic site is either created or stabilized in enzymatic conformations induced by substrate binding. In contrast to SIRT2, specific binding of [3H]AziPm or propofol to recombinant human SIRT1 was not observed. Residues that line the propofol binding site on SIRT2 contact the sirtuin co-substrate NAD+ during enzymatic catalysis, and assays that measured SIRT2 deacetylation of acetylated α-tubulin revealed that propofol inhibits enzymatic function. We conclude that propofol inhibits the mammalian deacetylase SIRT2 through a conformation-specific, allosteric protein site that is unique from the previously described binding sites of other inhibitors. This suggests that propofol might influence cellular events that are regulated by protein acetylation state.