Tunicamycin inhibits GlcNAc-lipid formation in plants

Previous studies from this laboratory (Forsee, W. T., and Elbein, A. D. (1975) J. Biol. Chem. 250, 9283-9293; Forsee, W. T., Valkovich, G., and Elbein, A. D. (1976) Arch Biochem. Biophys. 174, 469-479) have shown that particulate extracts from cotton fibers and mung been seedlings catalyze the transfer of mannose from GDP-[14C]mannose and GlcNAc from UDP-[3H]GlcNAc into lipid-linked saccharides, Concentrations of tunicamycin of 5 microgram/ml or higher inhibit the incorporation of GlcNAc into GlcNAc-pyrophosphoryl-polyprenol but this antibiotic, even at 500 microgram/ml, had no effect on the synthesis of mannosyl-phosphoryldolichol. Tunicamycin also caused a slight inhibition in the incorporation of mannose into lipid-linked oligosaccharides. The concentration of tunicamycin necessary for inhibition was dependent on the amount of particulate enzyme in the incubations.