Different fates of the oligosaccharide moieties of lipid intermediates.
We have previously described that the N-glycosylation process was accompanied by the release of oligosaccharide-phosphates and neutral oligosaccharides. The relationship between oligosaccharide-P-P-dolichol and its metabolic products (glycoproteins, oligosaccharide-phosphates and neutral oligosaccharides) was investigated by analysing the structure of the oligosaccharide moieties and the kinetic behaviour of the various species in pulse and pulse/chase experiments. For these studies, a glycosylation mutant of Chinese hamster ovary cells (B3F7) which does not synthesize mannosylphosphoryldolichol was utilized. Evidence was obtained for the presence of two pools of oligosaccharide-P-P-dolichol which have different fates. One pool is not glucosylated, is rapidly labelled and immediately chased by mannose, and generates the oligosaccharide-phosphate species. The second pool is glucosylated, exhibits a lag time (5-10 min) prior to being labelled, and is utilized in the glycosylation of proteins and in the production of neutral oligosaccharides. We postulate that the cleavage of non-glycosylated lipid intermediates generating oligosaccharide-phosphates represents a 'bypass' in the dolichol cycle which allows direct regeneration of dolichyl phosphate. The other metabolic fate of non-glucosylated oligosaccharide-lipids, glucosylation, results in their use as effective substrates for the glycosylation of proteins or in the generation of neutral oligosaccharides.
Cacan
R
R
Laboratoire de Chimie Biologique, UMR no. 111 du CNRS, Villeneuve d'Ascq, France.
Villers
C
C
Bélard
M
M
Kaiden
A
A
Krag
S S
SS
Verbert
A
A
D000818:Animals; D016466:CHO Cells / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D004287:Dolichol Monophosphate Mannose / Q000737:chemistry; D004288:Dolichol Phosphates / Q000737:chemistry; D006031:Glycosylation; D006863:Hydrogen-Ion Concentration; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism*; D051381:Rats
D004288:Dolichol Phosphates; D008055:Lipids; D009844:Oligosaccharides; D004287:Dolichol Monophosphate Mannose