Sialic acid

Sialic acids (synonym: sialic acid, σίαλον from the Greek word / sialon for saliva) is the generic term for the N -and O- derivatives of neuraminic acid ( Acylneuraminsäure ). Often occurring in the human N- acetylneuraminic acid ( NeuNAc or NANA ) is referred to as sialic acid. However, the term also includes a number of other sialic Neuraminsäurederivate, even if N-acetylneuraminic acid is the most abundant. These derivatives include, for example occurring in the mice N- glycolylneuraminic acid.

Occurrence

N-acetylneuraminic acid is a characteristic part of amino sugars, which are for the cell -cell interactions of significance. Sialic acid is used, among other things, protect the protein from degradation by proteases.

As a natural element it comes as a prosthetic group present in glycoproteins and in gangliosides ( glycolipids ) and is to be found esp. in glandular secretions, cell membranes and blood plasma. Sialic acid glycoproteins ( sialoglycoproteins ) are essential components of mucins ( mucins ) and enzymes such as lysosomal phosphatases, kallikrein, erythropoietin, follicle stimulating hormone ( FSH), as well as transport and Resorptionsproteinen as ceruloplasmin (CP ) and transferrin. The α -glucosidic bonds of sialic acids can be cleaved by neuraminidase. A recent example of the importance of sialic acid are derived from the sialic acid neuraminidase inhibitors zanamivir and oseltamivir, which are used as active agents against influenza.

In the cell walls of E. coli bacteria Sialic acid is a building block of the polysaccharide is colominic acid, N -acetyl- neuraminic acid polymer.

Sialic acid residues are also found on erythrocytes, but they lose this time. So aged erythrocytes are broken down in the spleen by macrophages.