Neuraminidase
From Wikipedia, the free encyclopedia
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sialidase 1 (lysosomal sialidase)
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| Identifiers | |
| Symbol(s) | NEU1 NEU |
| Entrez | 4758 |
| OMIM | 608272 |
| RefSeq | NM_000434 |
| UniProt | Q99519 |
| Other data | |
| EC number | 3.2.1.18 |
| Locus | Chr. 6 p21 |
Neuraminidase is a glycoside hydrolase enzyme (EC 3.2.1.18). It is frequently found as an antigenic glycoprotein and is best known as one of the enzymes found on the surface of the Influenza virus. Some variants of the influenza neuraminidase confer more virulence to the virus than others. At least four neuraminidases in the human genome have been described. Deficiencies in the human enzyme NEU1 leads to the rare lysosomal storage disease sialidosis (Mendelian Inheritance in Man (OMIM) 256550).
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[edit] Subtypes
Swiss-Prot lists 137 types of neuraminidase from various species as of October 18, 2006 [1]. Nine subtypes of influenza neuraminidase 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.
[edit] Structure
Influenza neuraminidase 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.
[edit] 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 many bacteria including 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.
[edit] Neuraminidase inhibitors
Several competitive neuramindase inhibitors are useful for combating influenza infection. They are zanamivir, administered by inhalation, and oseltamivir, administered orally.
[edit] See also
- Hemagglutinin
- Antigenic shift
- glucoside hydrolase
- H5N1 genetic structure
