Histone deacetylase that catalyzes the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events. Histone deacetylases act via the formation of large multiprotein complexes. Also involved in the deacetylation of non-histone proteins. In addition to protein deacetylase activity, also has protein-lysine deacylase activity: acts as a protein decrotonylase by mediating decrotonylation ((2E)-butenoyl) of histones. H2O + N(6)-acetyl-L-lysyl-[histone] = acetate + L-lysyl-[histone] H2O + N(6)-acetyl-L-lysyl-[protein] = acetate + L-lysyl-[protein] H2O + N(6)-(2E)-butenoyl-L-lysyl-[protein] = (2E)-2-butenoate + L-lysyl-[protein] Binds 1 divalent metal cation per subunit. Its activity is inhibited by trichostatin A (TSA) and butyrate, 2 well known histone deacetylase inhibitors. Excluded from the nucleoli. Found in the cytoplasm of cells showing smooth muscle differentiation. Belongs to the histone deacetylase family. HD type 1 subfamily.