Sialic acids
Sialic acids (synonym: sialic acid , from the Greek word σίαλον / sialon for saliva ) is the generic term for the N - and O -derivatives of neuraminic acid (acylneuraminic acid). The N-acetylneuraminic acid ( NeuNAc or NANA ) found in humans is often referred to as sialic acid. The term sialic acid also includes a number of other neuraminic acid derivatives, even if N-acetylneuraminic acid is the predominant one. These derivatives include, for example, N-glycolyl neuraminic acid, which occurs in mice .
Occurrence
N-acetyl neuraminic acid is a characteristic component of amino sugars , which are important for cell-cell interactions . Sialic acid serves, among other things, to protect proteins from degradation by proteases .
As a natural component it occurs as a prosthetic group in glycoproteins and in gangliosides ( glycolipids ) and is v. a. found in glandular secretions , cell membranes and blood plasma . Sialic acid-containing glycoproteins (sialoglycoproteins) are essential components of mucous substances ( mucins ) and of enzymes such as lysosome phosphatases , kallikrein , erythropoietin , follicle-stimulating hormone (FSH) and transport and absorption proteins such as ceruloplasmin (CP) and transferrin . The α-glycosidic bonds of sialic acids can be cleaved by neuraminidases . A current example of the importance of sialic acid are the neuraminidase inhibitors zanamivir and oseltamivir , which are derived from sialic acid and are used as active ingredients against influenza .
In the cell walls of coliform bacteria Sialic acid is a building block of the polysaccharide colominic acid , a N -acetyl-neuraminic acid polymer .
Sialic acid residues are also found on erythrocytes , but they lose them over time. Erythrocytes aged in this way are broken down in the spleen by macrophages .
literature
- Rudolf Jäckh: Chemistry and Biology of Sialic Acids . In: Chemistry in Our Time . tape 10 , no. 5 , 1976, p. 139-146 , doi : 10.1002 / ciuz.19760100503 .
