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:[7]
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.[8]
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 aminebase. 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.[10][11]
For example, salicylic acid can be acetylated by acetic anhydride to form aspirin:[12]
Pharmacology
Acetylated organic molecules exhibit increased ability to cross the selectively permeable blood–brain barrier.[13] Acetylation helps a given drug reach the brain more quickly, making the drug's effects more intense and increasing the effectiveness of a given dose.[citation needed] The acetyl group in acetylsalicylic acid (aspirin) enhances its effectiveness relative to the natural anti-inflammatantsalicylic acid. In similar manner, acetylation converts the natural painkiller morphine into the far more potent heroin (diacetylmorphine).[13]
There is some evidence that acetyl-L-carnitine may be more effective for some applications than L-carnitine.[14] Acetylation of resveratrol holds promise as one of the first anti-radiation medicines for human populations.[15]
Etymology
The term "acetyl" was coined by the German chemist Justus von Liebig in 1839 to describe what is now known as the vinyl group (coined in 1851). He and others before him regarded this group (groups were called radicals at that time) as the basis for other C2 compounds including acetic acid (the main component of vinegar, aside from water), Later the name was carried over to the MeCO-group used today, but the name of acetylene (coined in 1860) was retained.[16] "Acetyl" is derived from the Latin acētum, meaning "vinegar.", and the Greek Húlē, meaning substance, or material.[17]
↑"R-5.7.1 Carboxylic acids, where acetyl appears as an example". IUPAC, Commission on Nomenclature of Organic Chemistry. A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993), 1993, Blackwell Scientific publications, Copyright 1993 IUPAC.
↑Liu, J; Head, E; Kuratsune, H; Cotman, C. W.; Ames, B. N. (2004). "Comparison of the effects of L-carnitine and acetyl-L-carnitine on carnitine levels, ambulatory activity, and oxidative stress biomarkers in the brain of old rats". Annals of the New York Academy of Sciences. 1033 (1): 117–31. Bibcode:2004NYASA1033..117L. doi:10.1196/annals.1320.011. PMID15591009. S2CID24221474.
