Neuraminidases ( sialidases ) are split off a family of enzymes, the sialic acids from amino- glycoproteins and thus make this digestible. Such enzymes are commonly found in viruses, bacteria, protozoa and other parasites and fungi, but also occur in the lysosomes and the cell membranes of animals and humans. Here they are indispensable in reducing the corresponding Aminoglycoproteine ​​and membrane gangliosides. A deficiency disease leads to increased content of these substances in blood and urine ( Sialidosis ).

Virus enzyme

Neuraminidase ( measles, mumps, influenza type A and B and others) are firmly anchored in the membrane of many ortho-and paramyxoviruses. They split glycoproteins of the membranes of viruses and host cells viruses themselves, to free himself after the duplication of the infected cell.

So-called neuraminidase inhibitors are drugs that slow down the process of elimination of the host cell after infection with influenza viruses. As it is generally important to take the medication within the first 48 hours after the first symptoms. This type of drug, oseltamivir and zanamivir for the part, hope to be able to effect a first containment during a possible pandemic influenza A/H5N1 virus is through the.

There are nine influenza A neuraminidase types that are designated as N1 -9. The common name combination HxNy ( eg H5N1 ) results in combination with another surface protein, called hemagglutinin, and referred to the appropriate present on the surface of the viral proteins that are crucial necessary in the host cell penetration.


In bacteriophages of the K1 family a Endosialidase was identified. In contrast to classical Sialidases example, influenza viruses A Endosialidase ( Endon ) splits non-terminal sialic acid residues of glycoconjugates, but only inside of sialic acid homo- oligomers and homo- polymers ( polySia ).

The crystal structure of a Endosialidase was established in 2005.

Bacteria and parasites

Several indications that sialidases important for the feeding of many types of bacteria, in particular intestinal bacteria are, and the fact that many pathogenic microorganisms have sialidase activity, show that the enzyme also plays an important role in bacterial metabolism. The same relationship between sialidase activity and pathogenicity could be the causative agent of Chagas' disease to determine ( Trypanosoma cruzi ).


Sialidases make up the family 33 in the classification of glycosidases by Henrissat.