Membrane preparations from growing regions of pea stems and activelydividing mouse L-cells form lipid-linked saccharides from GDP-mannose and UDP-N-acetylglucosamine. These lipids have properties which are consistent with those of mono-and di-phosphoryl polyisoprenyl derivatives.
In experiments using plant membranes, the monophosphoryl derivative labeled with GDP-(14C) mannose contains mannose only, while the diphosphoryl derivative labeled with the same nucleotide sugar is heterogeneous, containing oligosaccharides corresponding t o mannosaccharides of 5, 7, and 9-12 residues. Only the diphosphoryl polyisoprenyl derivatives are labeled with UDP-( ''C)glucosamine and these contain predominantly chitobiose and Nacetylglucosamine itself. Unlabeled GDP-mannose added after UDP-N-acetyl-( 14C)glucosamine results in the formation of higher lipid-linked oligosakcharides which are apparently the same as those which are labeled with GDP-(14C)mannose alone. Incubation of the membranes with GDP-( ''C)mannose in the presence of MnZ+, unlabeled UDP-glucose or unlabeled UDP-N-acetylglucosamine results in marked changes in the accumulation of both the polyisoprenyl monophosphoryl mannose and polyisoprenyl diphosphoryl oligosaccharides.
Animal cell membranes synthesise lipid-linked oligosaccharides when incubated with UDP-N-acetylglucosamine and GDP-mannose. These oligosaccharides are similar in size t o those synthesised by the plant membranes but their formation is more efficient. The potential roles of these compounds in glycoprotein biosynthesis in both plant and animal tissues is discussed.