Low Na+ (5×10-5M) and higher K+ or divalent cation concentration (5×10-4M) fully activate synaptic membrane sialidase towards exogenous gangliosides. As the concentration of Ca++ or Zn++ is increased above 510-4M, exogenous sialidase activity is inhibited. Increased Na+ or K+ concentrations do not give this effect. Activity towards endogenous gangliosides is not controlled by external cations. Both endogenous and exogenous activities are optimum over a narrow pH range, 3.9 to 4.5, and activity is low above 6 or below 2. These results suggest that pH and ionic flux may regulate the density of fixed negative charge due to bound sialic acid in the synapse, and influence synaptic transmission, by controlling the separate actions of synaptic membrane sialidase.
|Original language||English (US)|
|Number of pages||7|
|Journal||Biochemical and Biophysical Research Communications|
|State||Published - Mar 3 1975|
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology