Enhancement and stabilization effect of EDTA on Sendai virus neuraminidase activity

EDTA was found to enhance, and exert a stabilizing effect on, Sendai virus neuraminidase activity. The effect was dependent on the molecular form of the enzyme and on the nature of the substrate. The "native form" (enzyme bound to the virions) was less influenced than the "mixed form" (enzyme separated from the surface of virions together with other glycoproteins), which in turn was less influenced than the purified enzyme. On the other hand, the stimulation by EDTA of neuraminidase-induced hydrolysis of fetuin was higher than that of ovomucoid. The kinetic data obtained indicate that EDTA modifies the enzyme in such a manner that the affinity of the substrate for the enzyme is increased.