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Desialylation of extracellular GD1a‐neoganglioprotein suggests cell surface orientation of the plasma membrane‐bound ganglioside sialidase activity in human neuroblastoma cells
Author(s) -
Kopitz Jürgen,
Oehler Christian,
Cantz Michael
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02207-4
Subject(s) - sialidase , ganglioside , endocytosis , substrate (aquarium) , cholera toxin , chemistry , extracellular , biochemistry , membrane , in vitro , enzyme , cell membrane , neuroblastoma , cell , biophysics , cell culture , microbiology and biotechnology , biology , neuraminidase , ecology , genetics
The orientation of the catalytic site of a ganglioside‐specific sialidase in the plasma membrane of SK‐N‐MC neuroblastoma cells was probed using water‐soluble GD1a‐neoganglioprotein substrate on intact cells and GM1‐product detection by cholera toxin B. Desialylation of substrate was readily observed, whereas specific sialidase inhibitors prevented the reaction, and conditioned medium was inactive. Inhibitors of endocytosis and acidification had no effect on substrate degradation, and lowering temperature to 18°C reduced activity but did not abolish it. We conclude that the ganglioside sialidase activity is cell surface‐orientated and displays an in situ specificity that mirrors enzyme preparations in vitro.