Neuraminidase

Neuraminidase is an antigenic glycoprotein enzyme () found on the surface of the Influenza virus.

Subtypes

Nine neuraminidase subtypes are known; many occur only in various species of duck and chicken. Subtypes N1 and N2 have been positively linked to epidemics in man, and strains with N3 or N7 subtypes have been identified in a number of isolated deaths.

Structure

The neuraminidase enzyme exists as a mushroom-shape projection on the surface of the influenza virus. It has a head consisting of four co-planar and roughly spherical subunits, and a hydrophobic region that is embedded within the interior of the virus' membrane. It is comprised of a single polypeptide chain that is oriented in the opposite direction to the hemagglutinin antigen. The composition of the polypeptide is a single chain of six conserved polar amino acids, followed by hydrophilic, variable amino acids.

Function

Neuraminidase has functions that aid in the efficiency of virus release from cells. Neuraminidase cleaves terminal sialic acid residues from carbohydrate moieties on the surfaces of infected cells. This promotes the release of progeny viruses from infected cells. Neuraminidase also cleaves sialic acid residues from viral proteins, preventing aggregation of viruses. Administration of chemical inhibitors of neuraminidase is a treatment that limits the severity and spread of viral infections.

Neuraminidase is also a virulence factor for the bacteria Bacteroides fragilis.

Ideally influenza virus neuraminidase NA should act on the same type of virus receptor the virus hemagglutinin HA binds to. This is not always so. It is not quite clear how the virus manages to function if there is no close match between the specificities of NA and HA

Neuraminidase inhibitors

Inhibitors are used for combating the virus. They are zanamivir and oseltamivir.

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Subtypes

Structure

Function

Neuraminidase inhibitors

See also