Catalytic Activity of HDAC11 and HDAC8

Histone deacetylases (HDACs) catalyze the deacetylation of acetylated lysine residues on histone proteins. In general, increased HDAC activity results in the silencing of genes; and HDAC inhibitors have been implicated in apoptosis, making them attractive anti‐cancer drugs. Metal‐dependent HDACs have been divided into two classes, based on sequence homology. HDAC11 is not yet characterized, but contains conserved residues present in both classes of HDACs. Human HDAC11 has been recombinantly expressed in E. coli. The catalytic activity of this isozyme for deacetylating the peptide substrate (R‐H‐K(Ac)‐K(Ac)‐fluorophore) is 5‐fold lower than that of HDAC8. The activity of HDAC11 is activated by metal ions; the activity of Co2+‐substituted HDAC11 is 15‐fold larger than the activity of the zinc‐bound enzyme, comparable to the metal dependent activation of HDAC8. Also SAHA, an approved cancer drugs, inhibits metal‐bound HDAC11 with μM affinity. In HDAC8, Arginine 33 is positioned in a cavity that is perpendicular to the substrate‐binding site in HDAC8. Computational studies implicate this residue in modulating the dissociation of the acetate product from the active site. Removal of this side chain in the Arg33Ala mutation decreases catalytic activity by 1000‐fold, retains wild‐type structure, and eliminates inhibition by acetate.