Histone deacetylases (EC3.5.1.98, HDAC) are a class of enzymes that remove acetyl groups (O=C-CH3) from an ε-N-acetyl lysineamino acid on both histone and non-histone proteins.[2] HDACs allow histones to wrap the DNA more tightly.[3] This is important because DNA is wrapped around histones, and DNA expression is regulated by acetylation and de-acetylation. HDAC's action is opposite to that of histone acetyltransferase. HDAC proteins are now also called lysine deacetylases (KDAC), to describe their function rather than their target, which also includes non-histone proteins.[4] In general, they suppress gene expression.[5]