Plant glycolipids

Abstract

The complex nature of the glycolipids from mung bean has been examined. The lipid-bound monosaccharides are similar to the mono-saccharides constituents of polysaccharides which occur commonly in the plant kingdom. The glycosyl groups in the lipids appear to be acid labile and are bound as glycosylglycerides and as non-saponifiable glycolipids.Glycolipids in mung bean do not seem to be associated with a definite particulate fraction. Glycosylglycerides with relatively short sugar chains have been identified; glucose and fructose are the two main monosaccharide constituents of these lipids. A fructolipid containing a 2,3-linked furanose ring system has been isolated. Arabinose, most of the galactose, mannose and rhamnose all appear to be associated with a non-saponifiable lipid fraction.A preliminary investigation of the incorporation of label from sucrose-14C into the glycosyl residues of mung bean lipids showed that they became rapidly labelled and there was a tendency for the monosaccharides bound to non-saponifiable lipids to have the highest specific activities. Glucose fructose and mannose may be raetabolicallymore active than galactose, arabinose and rhamnose. The latter sugars< may be components of a structural lipid.As a preliminary to examining the pathway for the formation of the fructolipid present in mung bean shoots, the enzyme synthesis of UDP-fructose, a likely precursor, was studied. The results suggest that fructose-2-phosphate is the probable substrate for a UDP-fructose pyrophosphorylase and that tissue extracts contain a phospho-fructorautase which can convert fructose-l-phosphate to fructose-2-phosphate. The nature of the linkage between UDP and fructose has not been established beyond doubt, however.