Neuraminidases (sialidases) hydrolyse the non-reducing, terminal sialic acid linkage in various natural substrates, such as glycoproteins, glycolipids, gangliosides, and polysaccharides . In mammals, neuraminidases occur in the lysosome, the cytosol, and associated with the plasma membrane. Neuraminidases have also been implicated in the pathogenesis of many diseases. For example, in viruses neuraminidases enable the transport of the virus through mucin, the eruption of the virus from the infected host cell, and the prevention of self-aggregation of virus particles through the destruction of the host cell receptor recognised by the virus . Eukaryotic, bacterial and viral neuraminidases share highly conserved regions of beta-sheet motifs. Bacterial neuraminidases often possess domains in addition to the catalytic neuraminidase domain, for instance the neuraminidase from Micromonospora viridifaciens contains three domains, of which the catalytic domain described here is the N-terminal domain . Similarly, leech neuraminidase is a multidomain protein, where the catalytic domain is the C-terminal domain . In several paramyxoviruses, neuraminidase forms part of the multi-functional haemagglutinin-neuraminidase glycoprotein found on the viral envelope .