Rat brain microsomal gangliosides. Accessibility to a neuraminidase preparation and the possible existence of different pools in relation to their biosynthesis.
1. Treatment of rat brain microsomal membranes with a neuraminidase preparation from Clostridium perfringens resulted in an almost complete conversion of polysialogangliosides into monosialogangliosides. 2. Neuraminidase treatment of the membranes did not increase the incorporation of N-[(3)H]acetylneuraminic acid from CMP-N-[(3)H]acetylneuraminic acid into the gangliosidic fraction, indicating that a monosialoganglioside is an acceptor of N-acetylneuraminic acid in these membranes only if, in addition to having the right chemical structure, it is in a proper position, probably in relation to the endogenous sialyltransferases. 3. These experiments also indicated that no independent turnover of the neuraminidase-labile N-acetylneuraminyl groups of gangliosides occurred in vitro. 4. N-[(3)H]Acetylneuraminic acid from endogenous polysialogangliosides labelled in vitro was released by neuraminidase at a slower rate than N-acetylneuraminic acid from unlabelled gangliosides of the same membranes. From this it was concluded that recently synthesized polysialogangliosides (completed in vitro) are in the membranes in a position less accessible to neuraminidase than are those synthesized earlier which were present in the membranes at the start of the labelling experiment.
D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D001923:Brain Chemistry; D002250:Carbon Radioisotopes; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D002855:Chromatography, Thin Layer; D003016:Clostridium perfringens / Q000201:enzymology; D003597:Cytosine Nucleotides; D005732:Gangliosides / Q000378:metabolism*; D007700:Kinetics; D008566:Membranes / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism*; D009438:Neuraminic Acids / Q000032:analysis; D009439:Neuraminidase; D051381:Rats; D013696:Temperature; D013997:Time Factors; D014316:Tritium; D014465:Ultrasonics
D002250:Carbon Radioisotopes; D003597:Cytosine Nucleotides; D005732:Gangliosides; D009438:Neuraminic Acids; D014316:Tritium; D009439:Neuraminidase