Biosynthesis of lipid-linked oligosaccharides in embryonic liver. Formation of mannose containing derivatives

In the presence of exogenous dolichyl phosphate mannosyl transferase activity towards dolichyl phosphate was nearly 3-fold higher in microsomes from pig embryonic liver compared to that from adult liver. After incubation of microsomes from embryonic liver with UDP-N-acetylglucosamine and GDP-[14C]mannose lipid-linked tri- to undecasaccharides were discovered in CHCl3-CH3OH (2:1, v/v) and CHCl3-CH3OH-H2O (1:1:0.3, by vol) extracts. The main proportion of the radioactivity was incorporated into penta-, sexta and undecasaccharides. Amphomycin at concentration 500 micrograms/ml inhibited almost completely dolichyl phosphate mannose synthesis in embryonic liver microsomes without inhibition the formation of lipid-linked penta- and sextasaccharides. It was suggested that mannose transferred to lipid-linked tetra- to heptasaccharides comes from GDP-mannose but not from dolichyl phosphate mannose.