Plant Glycolipids

Lipids include fatty acids (aliphatic carboxylic acids), fatty acid esters, phospholipids, and glycolipids. Plants containing lipids with anticancer properties include the following ... 

Glycolipids consist of a sugar moiety attached to the glycerol backbone and are abundantly found in some algae, higher plant tissues, and microorganisms, whereas they may be present, if at all, only as trace constituents in animal tissues. 

Two-dimensional techniques are usually employed if both phospho-glycerides and glycolipids are present, but it is possible to resolve members of both classes using a diisobutylketone-acetic acid-water mixture (40 25 5). A solvent composed of acetone, acetic acid and water (100 2 1) will separate the mono- and di-galactosyldiglycerides, which are particularly abundant in plant extracts, from phosphoglycerides, which remain at the origin. 

Lipid transfer peptides and proteins occur in eukaryotic and prokaryotic cells. In vitro they possess the ability to transfer phospholipids between lipid membranes. Plant lipid transfer peptides are unspecific in their substrate selectivity. They bind phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and glycolipids. Some of these peptides have shown antifungal activity in vitro The sequences of lipid transfer proteins and peptides contain 91-95 amino acids, are basic, and have eight cysteine residues forming four disulfide bonds. They do not contain tryptophan residues. About 40% of the sequence adopts a helical structure with helices linked via disulfide bonds. The tertiary structure comprises four a-helices. The three-dimensional structure of a lipid transfer peptide from H. vulgare in complex with palmitate has been solved by NMR. In this structure the fatty acid is caged in a hydrophobic cavity formed by the helices. 

Mudd, J. B.. T. T. McManus, A. Ongun, and T. E. McCullough. Inhibition of glycolipid biosynthesis in chloroplasts by ozone and sulfhydryl reagents. Plant Physiol. 48 335-339, 1971. 

One major pathway leads from acetyl-CoA to the activated fatty acids (acyl-CoA for details, see p.l68). Fats, phospholipids, and glycolipids are synthesized from these, and fatty acid derivatives in particular are formed. Quantitatively, this is the most important pathway in animals and most plants. 

Note Values do not add up to 100% in every case, because there are components other than protein, phospholipids, and sterol plants, for example, have high levels of glycolipids. 

The involvement of glycolipid and glycoprotein intermediates in the synthesis of polysaccharides from glycosyl-nucleotides in plants is considered to be a likely possibility. Such intermediates could act as specific primers, or acceptor substrates, for the formation of polysaccharides. Furthermore, subunits of complex heteropolysaccharides could be assembled on such intermediates, and later incorporated into polysaccharides, or directly cross-linked into the cell wall. Evidence of the involvement of such intermediates in the synthesis of polysaccharides in a number of organisms is presented in Sections XII,3,b and XII,3,c. 

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