Neuraminidases

Neuraminidases are a family of enzymes of influenza (type A and B) and other viruses. Neuraminidase (NA) is the second most abundant influenza surface glycoprotein (after hemagglutinin) and contributes to virus replication in several ways, in particular by removing sialic acids from the glycoproteins of the host and the virus. This process promotes the release of daughter viruses from the infected cells.

Neuraminidases are also found in bacteria, other protozoa, parasites and fungi, but are also present in the lysosomes and cell membranes of animals and humans. Here they are indispensable for the degradation of the corresponding aminoglycoproteins and membrane gangliosides. A deficiency disease leads to increased levels of these substances in the blood and urine (sialidosis).

The so-called neuraminidase inhibitors are drugs that slow down this process of splitting off from the host cell after an infection with influenza viruses. It is generally important to take the medication within the first 48 hours after the first symptoms appear. This type of medication, which includes Tamiflu and Relenza, is hoped to provide initial containment in the event of an influenza A/H5N1 pandemic.

Although neuraminidases are described as receptor-disrupting enzymes, human H3N2 viruses with low or undetectable NA activity have been isolated in recent years due to large deletions of the coding sequence that remove most or all of the catalytic head domain (Air GM 2012).

The name neuraminidase is derived from the alternative name of sialic acid, N-acetylneuraminic acid (NeuAc). Neuraminidase inhibitors are sialic acid analogs.

1. Air GM (2012). Influenza neuraminidase. Influenza Other Respir Viruses 6:245-256.
2. Bonten E et al. (1996) Characterization of human lysosomal neuraminidase defines the molecular basis of the metabolic storage disorder sialidosis. In: Genes & development. Volume 10, Number 24: 3156-3169.
3. Eichelberger MC et al. (2015) Influenza neuraminidase as a vaccine antigen. Curr Top Microbiol Immunol 386:275-99.
4. Eichelberger MC et al. (2018) Neuraminidase as an influenza vaccine antigen: a low hanging fruit, ready for picking to improve vaccine effectiveness. Curr Opin Immunol 53:38-44.