FORMATION OF DOLICHOL MONOPHOSPHATE 2-DEOXY-D-GLUCOSE AND ITS INTERFERENCE WITH GLYCOSYLATION OF MANNOPROTEINS IN YEAST

A crude membrane fraction from Saccharomyces cerevisiae was found to catalyze 2-deoxy-D-glucose transfer from GDP-2-deoxy-D-glucose to endogenous lipid and glycoprotein acceptor. The glycolipid formed has properties characteristic of dolichol monosphosphate 2-deoxy-D-glucose. The 2-deoxy-D-glucosyl group can further be transferred from the glycolipid into a membrane-bound polymer fraction. More than 95% of the radioactivity incorporated can be released by .beta.-elimination, indicating an O-glycosidic linkage to serine or threonine. The only radioactive product obtained is 2-deoxy-D-glucose. When dolichol monophosphate 2-deoxy-[14C]glucose is incubated together with non-radioactive GDP-mannose subsequent .beta.-elimination yields no higher oligosaccharides in contrast to an experiment where dolichol monophosphate [14c]mannose and GDP-mannose are used as donors. The non-physiological nucleotide sugar apparently interferes with GDP-mannose for mannosylation and terminates further elongation of the serine/threonine-bound oligomannose side chains. UDP-2-deoxy-D-glucose, used as donor, results in the formation of a glycolipid. In this case, no polyprenol derivative is formed. Instead, the glycolipid displays properties characteristic of a sphingolipid or a sterol glucoside.