Properties of endogenous, membrane-associated sialidase activity (N-acetylneuraminidase) of the goldfish visual system.

The endogenous sialidase (N-acetylneuraminidase) activity of membranes prepared from goldfish retina and optic tectum displays characteristics similar to those reported for neural plasma membrane sialidases of other organisms. Endogenous membrane sialidase activity was found to be optimal at ph 4.0, and maximal release was obtained at 37-50 degrees C, above which temperature thermal instability of the preparations was observed. Optic nerve crush, which results in regeneration of retinal ganglion cell axons, did not result in significant changes in measured endogenous membrane sialidase activity in either the retina or the optic tectum. Enzymatic hydrolysis of membrane sialoglycolipid (ganglioside) accounted for about 70% of the total sialic acid released. Ganglioside GM1 accumulated as the major lipid product in both retina and tectum, indicating that the inner sialosylgalactosyl linkage in the ganglio oligosaccharide series was resistant to hydrolysis by the endogenous enzyme.