Acetyl group known as paracetamol), and acetylsalicylic acid (better known as aspirin). The introduction of an acetyl group into a molecule is called acetylation. In biological organisms, acetyl groups are commonly transferred from acetyl-CoA to other organic molecules. Acetyl-CoA is an intermediate both in the biological synthesis and in the breakdown of many organic molecules. Acetyl-CoA is also created during the second stage of cellular respiration, the Krebs Cycle, by the action of pyruvate dehydrogenase on pyruvic acid. Histones and other proteins are often modified by acetylation. For example, on the DNA level, histone acetylation by acetyltransferases (HATs) causes an expansion of
Neuraminic acid considerably: acetyl, lactyl, methyl, sulfate and phosphate groups have been found. The name "neuraminic acid" was introduced by German scientist E. Klenk in 1941, in reference to the brain lipids from which it was derived as a cleavage product. The symbol commonly used for neuraminic acid is Neu, and the residue is typically found with additional chemical modifications in biological systems. As a family, these residues are known as sialic acids. For example, "N"-acetylneuraminic acid, Neu5Ac, is typical in human glycoproteins. Among their many biological functions, these structures are substrates for neuraminidase enzymes which cleave neuraminic acid residues. Human flu