Acetylation is the chemical reaction known as "ethanoylation" in the IUPAC nomenclature. It depicts a reactionary process that injects an acetyl functional group into a chemical compound. The opposite reaction is called "
deacetylation", and this is the
removal of the acetyl group. An example of an acetylation reaction is the conversion of
glycine to
N-acetylglycine: :
In biology Enzymes which perform acetylation on proteins or other biomolecules are known as
acetyltransferases. In biological organisms, acetyl groups are commonly transferred from
acetyl-CoA to other organic molecules. Acetyl-CoA is an intermediate in the biological synthesis and in the breakdown of many organic molecules. Acetyl-CoA is also created during the second stage of cellular respiration (
pyruvate decarboxylation) by the action of
pyruvate dehydrogenase on
pyruvic acid.
Proteins are often modified via acetylation, for various purposes. For example, acetylation of
histones by
histone acetyltransferases (HATs) results in an expansion of local
chromatin structure, allowing
transcription to occur by enabling
RNA polymerase to access
DNA. However, removal of the acetyl group by
histone deacetylases (HDACs) condenses the local chromatin structure, thereby preventing transcription.
In synthetic organic and pharmaceutical chemistry Acetylation can be achieved by chemists using a variety of methods, most commonly with the use of
acetic anhydride or
acetyl chloride, often in the presence of a tertiary or aromatic
amine base. Acetic anhydride and acetyl chloride are good candidates for acetylation for two reasons: the electrophilicity of the carbonyl carbon of the acetyl group is enhanced by the electron-withdrawing inductive effect of the neighbouring group (acetoxy- and chloro-, respectively), and the leaving group is stable or stabilised through resonance (acetate and chloride, respectively). The amine base is primarily used to capture free protons, but may also further activate the acetyl group towards nucleophilic attack. For example, salicylic acid can be acetylated by acetic anhydride to form aspirin: ==Pharmacology==