Neuraminidase of influenza A and B virus (NA)

Neuraminidase of influenza A and B viruses is a **surface glycoprotein enzyme (exosialidase, EC 3.2.1.18)** present on the exterior of the viral envelope[1][5]. Its main function is to catalyze the cleavage of terminal **sialic acid residues** from glycoproteins on the host cell and viral surfaces, which is essential for the release of newly formed viral particles from infected cells and for the efficient spread of the virus[2][3][5]. Structurally, NA is a tetrameric protein composed of four identical subunits (each ~470 amino acids), with distinct domains: cytoplasmic, transmembrane, stalk, and head[1][5]. There are nine major subtypes of NA in influenza A viruses (N1–N9) and one in B viruses; the structure is highly conserved despite sequence diversity[1][3][5][6]. NA is a validated **therapeutic target**: small molecule inhibitors (oseltamivir, zanamivir, peramivir) competitively block its enzymatic activity, thereby limiting virus spread and aiding host immune clearance[2][3][5][6]. However, mutations in NA can confer resistance to these drugs, presenting ongoing therapeutic challenges[2][6]. NA plays no significant role in non-infectious disease states; it is mainly implicated in the infection cycle, virulence, and transmissibility of influenza viruses. This information reflects the well-characterized nature of neuraminidase as a therapeutic drug target, its structural features, biological functions, and clinical relevance for both seasonal and pandemic influenza[1][2][3][5][6].

Other names

Influenza neuraminidaseViral neuraminidaseExosialidase (EC 3.2.1.18)SialidaseNA (subtypes: N1–N9 for influenza A; NA for B)

Competitive inhibition of neuraminidase active site to block sialic acid cleavage, preventing release and spread of the virus[2][3][5][6] Inhibition leads to reduced viral load and transmission