Neuraminidase

Neuraminidase Ribbon Diagram

Neu5Ac

Neuraminidase is an enzyme that plays a critical role in the life cycle of influenza viruses. It is found on the surface of influenza viruses and is responsible for cleaving sialic acid residues from glycoproteins, which facilitates the release of new virus particles from infected cells. This action is crucial for the spread of the virus within the host and is a target for antiviral drugs.

Function

Neuraminidase allows virus particles to be released from the host cell after replication and assembly. The enzyme cleaves sialic acid, which is found on the surface of cells in the respiratory tract, from glycoproteins. This cleavage prevents the newly formed viral particles from adhering to the infected cell, allowing them to spread to other cells and continue the infection cycle. Without neuraminidase, viruses would remain attached to the surface of the host cell, limiting their ability to spread and infect new cells.

Structure

Neuraminidase is a mushroom-shaped glycoprotein that protrudes from the viral envelope. It is typically composed of four identical subunits, and its active site, where sialic acid cleavage occurs, is located at the top of the structure. The structure of neuraminidase has been determined through X-ray crystallography, which has been instrumental in the design of neuraminidase inhibitors, a class of antiviral drugs.

Neuraminidase Inhibitors

Neuraminidase inhibitors are a class of antiviral drugs that target the neuraminidase enzyme, preventing it from cleaving sialic acid. This inhibition effectively stops the virus from spreading to other cells. Examples of neuraminidase inhibitors include oseltamivir (Tamiflu), zanamivir (Relenza), and peramivir (Rapivab). These drugs are used for the treatment and prevention of influenza A and B.

Clinical Significance

The role of neuraminidase in the spread of influenza has made it a target for vaccine development and antiviral therapy. Neuraminidase inhibitors are particularly useful in the management of influenza outbreaks and are recommended for both treatment and prophylaxis in high-risk populations. The effectiveness of these drugs can vary depending on the specific neuraminidase mutations present in circulating strains of the virus, highlighting the importance of ongoing surveillance and research.

Resistance

Resistance to neuraminidase inhibitors can occur through mutations in the neuraminidase gene. These mutations may alter the structure of the enzyme in a way that reduces the binding affinity of the inhibitors. Monitoring for resistance is an important aspect of influenza management and public health.