Further studies on a glycolipid formed from dolichyl-D-glucosyl monophosphate

Incubation of liver microsomes with dolichyl- d -glucosyl- 14 C monophosphate led to the labelling of an endogenous acceptor. This compound seems to be also a dolichol derivative. It contains a high-molecular weight oligosaccharide bound to dolichol through a phosphate or pyrophosphate bond. Various treatments of the labelled oligosaccharide afforded further information on its structure: Reduction with sodium borohydride, followed by acid hydrolysis gave only radioactive d -glucose indicating that the labelled d -glucose is not incorporated at the reducing end of the oligosaccharide. The percentage of radioactivity, liberated as formic acid after periodate oxidation, indicates that more than one molecule of d -glucose is incorporated and that at least one of them is inside the oligosaccharide chain. Alkaline treatment of the otherwise neutral oligosaccharide gave two positively charged derivatives which could be neutralized by N -acetylation, indicating the presence of two hexosamine residues. The oligosaccharides isolated from different tissues by the same method as that used for rat liver, were similar as judged by their migration in paper chromatography and by the pattern of products liberated by acetolysis.