Abstract
The neuraminidase activity of two strains of Duck/Mississippi/75 virus: DK/Mississippi/320 and DK/Mississippi/334 was studied. These neuraminidases hydrolyse the α 23 and α 28 ketosidic bonds of different substrates such as fetuin, N-acetyl neuramine lactose and colominic acid, but do not hydrolyse the α26 bonds of mucin type I and type II. The kinetic values of the neuraminidases, Michaelis constant, maximal and initial velocities and the effect of pH, temperature and detergents were also evaluated. The isolates differ mainly in the optimal pH and temperature conditions of activity. As with other paramyxovirus neuraminidases, the enzyme of DK/Mississippi/75 was destroyed by ionic but not non-ionic detergents.