Comparative rates of transfer of lipid-linked oligosaccharides to endogenous glycoprotein acceptors in vitro.

We have shown previously that particulate preparations of Nil 8 fibroblasts catalyze the synthesis of two oligosaccharide-lipids: one composed of N-acetylglucosamine and mannose residues and the other containing, in addition to mannose and N-acetylglucosamine, one or two glucose residues. These two oligosaccharide-lipids were purified and added to fresh microsomal preparations. In comparative studies, we find that the glucose-containing lipid-linked oligosaccharide is transferred much more rapidly to endogenous protein acceptors than the glucose-free compound. With materials of comparable specific activities, as much as 41% of the glucose-containing oligosaccharide was transferred to protein as compared to 5% for the glucose-free compound. These results suggest that the attachment of glucose to mannosyl lipid-linked oligosaccharide serves an important role in the transfer of these compounds from lipid carrier to protein acceptor.