What is "histone deacetylase"

n. (context enzyme English) Any of a class of enzymes that remove acetyl groups from lysine amino acids in proteins, especially the histone proteins of the nucleus

Histone deacetylases (, HDAC) are a class of enzymes that remove acetyl groups (O=C-CH) from an ε-N-acetyl lysine amino acid on a histone, allowing the histones to wrap the DNA more tightly. This is important because DNA is wrapped around histones, and DNA expression is regulated by acetylation and de-acetylation. Its 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.