Lipid‐Bound Oligosaccharides in Insects

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Abstract
Membrane preparations from immature stages of the fruit fly Ceratitis capitata catalyze the transfer of mannose from GDP‐[14C]mannose into lipid‐linked oligosaccharides. These compounds behave as polyprenyl derivatives and their formation is stimulated by the addition of an acidic glyco‐lipid fraction isolated from insects.The mannose‐labeled oligosaccharides are attached to the poly‐isoprenol by a pyrophosphoryl linkage and can be released by mild acid hydrolysis. The trisaccharide lipid has been partially characterized. The results indicate that the compound is polyprenyl‐pyrophosphate‐N,N′‐diacetylchitobiose‐mannose.Incubation of dolichyl phosphate [14C]mannose or lower 14C‐labeled oligosaccharide lipids with unlabeled GDP‐mannose and the insect enzyme leads to the labeling of a higher lipid‐bound oligosaccharide.When UDP‐N‐acetyl[14C]glucosamine was incubated with insect membranes a 14C‐labeled chitobiosyl lipid was synthesized. If unlabeled GDP‐mannose was also present, the 14C label appeared in the trisaccharide and higher oligosaccharide lipids.Preliminary evidence indicates that the insect polyprenyl oligosaccharides described here might participate in glycoprotein biosynthesis.