Possible Biological Roles for Viral Sialidases

While many roles have been proposed quite early for viral sialidase (viral penetration into the host cell, provision of lower-molecular-weight metabolites for viral propagation, release of newly formed virus from the host cell, destruction of substances which protect the cell surface from virus binding, viral binding to the host cell surface by enzyme-substrate interaction), conflicting lines of evidence for each hypothesis have prevented the certain adoption of any of them. For details in an old and a new review, see those by Kelly (1963) and Drzeniek (1972). More recently Tsvetkova and Lipkind (1973) have suggested that the viral 

The picture still is far from clear. The uniqueness of myxoviruses in having a surface enzyme such as sialidase lead one to presuppose that this enzyme helps to carry out a special myxoviral function. We propose a function different from those tested and found wanting. The newly synthesized sialidase molecules, for which the viral genome codes, moves to and is incorporated into the surface membrane of the host cell, and occupies a position similar to the native mammalian plasma membrane sialidase (see Section V). By removing contiguous sialic acid groups from the surface of the host cell membrane, the enzyme may serve to alter the physicochemical properties of the plasma membrane so 

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