acétylation

Acetylation is a chemical reaction in which an acetyl group (CH3CO-) is added to a substrate. This process is common in biological systems and plays a crucial role in regulating various cellular functions. In biochemistry, acetylation often refers to the addition of an acetyl group to a protein, typically on the nitrogen atom of a lysine residue or the oxygen atom of a serine or threonine residue. This modification can alter a protein's structure, stability, localization, and interaction with other molecules, thereby affecting its activity.

Enzymes called acetyltransferases catalyze acetylation reactions. For example, histone acetyltransferases (HATs) add acetyl groups to histones, proteins that package DNA. This histone acetylation generally loosens the chromatin structure, making DNA more accessible for transcription and thus promoting gene expression. Conversely, histone deacetylases (HDACs) remove acetyl groups, leading to chromatin condensation and gene silencing.

Beyond protein modification, acetylation is also involved in the metabolism of carbohydrates and lipids. Acetyl-CoA, a molecule that carries acetyl groups, is a central intermediate in cellular respiration, linking the breakdown of carbohydrates, fats, and amino acids to the citric acid cycle. Acetylation can also occur on small molecules like drugs, influencing their pharmacological properties, such as solubility and half-life. The reversibility of acetylation, mediated by enzymes like deacetylases, allows for dynamic control over biological processes.