Specifically, acetylation refers to that process of introducing an acetyl group (resulting in an acetoxy group) into a compound, namely, the substitution of an acetyl group for an active hydrogen atom. A reaction involving the replacement of the hydrogen atom of a hydroxyl group with an acetyl group (CH3 CO) yields a specific ester, the acetate. Acetic anhydride is commonly used as an acetylating agent reacting with free hydroxyl groups. For example, it is used in the synthesis of aspirin and heroin.
Acetylation of proteins
Acetylation is important in cell (biology) because acetyl groups can turn proteins and genes on and off.
Acetylation occurs as a co-translational and post-translational modification of proteins, for example, histones, p53, and tubulins. In fact, proteomics studies have identified thousands of acetylated mammalian proteins.  Among these proteins, chromatin proteins and metabolic enzymes are highly represented, indicating that acetylation has a considerable impact on gene expression and metabolism. In bacteria, 90% of proteins involved in central metabolism of Salmonella enterica are acetylated.
Acetylation of the amino terminus occurs in about 50% of yeast proteins and more than 80% of human proteins. The reaction is catalyzed by N-terminal acetyltransferases, occurs predominantly during protein synthesis and appears to be irreversible. Acetylation of the amino terminus of a protein can function as degradation signal (degron).
Lysine acetylation and deacetylation
Proteins are typically acetylated on lysine residues and this reaction relies on acetyl-coenzyme A as the acetyl group donor. In histone acetylation and deacetylation, histone proteins are acetylated and deacetylated on lysine residues in the N-terminal tail as part of gene regulation. Typically, these reactions are catalyzed by enzymes with histone acetyltransferase (HAT) or histone deacetylase (HDAC) activity, although HATs and HDACs can modify the acetylation status of non-histone proteins as well.
The regulation of transcription factors, effector proteins, molecular chaperones, and cytoskeletal proteins by acetylation and deacetylation is a significant post-translational regulatory mechanism  These regulatory mechanisms are analogous to phosphorylation and dephosphorylation by the action of kinases and phosphatases. Not only can the acetylation state of a protein modify its activity, there has been recent suggestion that this post-translational modification may also crosstalk with phosphorylation, methylation, ubiquitination, sumoylation, and others for dynamic control of cellular signaling.
The regulation of tubulin protein is an example of this in mouse neurons and astroglia. A tubulin acetyltransferase is located in the axoneme, and acetylates the α-tubulin subunit in an assembled microtubule. Once disassembled, this acetylation is removed by another specific deacetylase in the cell cytosol. Thus axonemal microtubules, which have a long half-life, carry a "signature acetylation" which is absent from cytosolic microtubules which have a shorter half-life.
- Choudhary C et al. (2009). "Lysine acetylation targets protein complexes and co-regulates major cellular functions.". Science 325 (5942): 834–40. doi:10.1126/science.1175371. PMID 19608861.
- Fritz KS et al. (2012). "Mitochondrial acetylome analysis in a mouse model of alcohol-induced liver injury utilizing SIRT3 knockout mice.". Journal of Proteome Research 11 (3): 1633–43. PMID 22309199. Text "10.1021/pr2008384 " ignored (help)
- Zhao S et al. (2010). "Regulation of cellular metabolism by protein lysine acetylation.". Science 327 (5968): 1000–1004. doi:10.1126/science.1179689. PMID 20167786.
- Mogk A, Bukau B. (2010). "Cell biology. When the beginning marks the end". Science 327: 966–967. doi:10.1126/science.1187274. PMID 20167776.
- Hwang, C.S. et al. (2010). "N-terminal acetylation of cellular proteins creates specific degradation signals". Science 327: 973–977. doi:10.1126/science.1183147. PMID 20110468.
- Sadoul K, Boyault C, Pabion M, Khochbin S (February 2008). "Regulation of protein turnover by acetyltransferases and deacetylases". Biochimie 90 (2): 306–12. doi:10.1016/j.biochi.2007.06.009. PMID 17681659.
- Glozak MA, Sengupta N, Zhang X, Seto E (2005). "Acetylation and deacetylation of non-histone proteins". Gene 363: 15–23. doi:10.1016/j.gene.2005.09.010. PMID 16289629.
- Yang XJ, Seto E (2008). "Lysine acetylation: codified crosstalk with other posttranslational modifications". Mol Cell 31 (4): 449–61. doi:10.1016/j.molcel.2008.07.002. PMC 2551738. PMID 18722172.
- Eddé, Bernard; et al. (1989). "Posttranslational modifications of tubulin in cultured mouse brain neurons and astroglia". Biology of the Cell 65: 109–117. Retrieved 2012-04-13.
- Maruta, H; et al. (1 August 1986). "The acetylation of alpha-tubulin and its relationship to the assembly and disassembly of microtubules". JBC 103 (2): 571–579. PMC 2113826. PMID 3733880.