histone deacetylase activity histone H3K deacetylase activity https://github.com/geneontology/go-ontology/issues/22836 molecular_function 2024-09-20T11:40:05Z Histone deacytylase (HDAC) enzymes are divided into four classes: the Class I Rpd3-like proteins (in human: HDAC1, HDAC2, HDAC3, and HDAC8); the Class II Hda1-like proteins (in human: HDAC4, HDAC5, HDAC6, HDAC7, HDAC9, and HDAC10); the Class III Sir2-like proteins (in human: SIRT1, SIRT2, SIRT3, SIRT4, SIRT5, SIRT6, and SIRT7); and the Class IV protein (HDAC11 in human). Except for Class III enzymes, the mechanism is a metal-dependent hydrolysis of the acetylated substrate. The Class III HDACs use NAD+ as a reactant to deacetylate acetyl lysine residues of protein substrates forming nicotinamide, the deacetylated product, and the metabolite 2'-O-acetyl-ADP-ribose. Therefore, Class III are classified as transferases (EC:2) and others are hydrolases (EC:3). Removal of an acetyl group from a lysine residue in a histone H3. GO:0141050 pg