Protein N-acetyltransferases catalyze the transfer of an acetyl group from acetyl-CoA (green, acetyl group in yellow) onto a substrate protein. An N-terminal acetyltransferase (NAT, top panel) targets the α-amino group (red) of the N-terminal residue, whereas a lysine acetyltransferase (KAT, bottom panel) targets the ε-amine group (red) of an internal lysine. targets. Lysines can be deacetylated by a lysine deacetylase (KDAC), while currently, no N-terminal deacetylases (NDACs) are known, and N-terminal acetylation is thus considered irreversible.