Cell Glycolipid

Fig. 7. Degradation of red cell glycolipids and formation of cerebrosides. Pathway A proposed by Philippart et al. (1965) pathway B proposed by Statter and Shapiro (1965). The suspected location of the lesion in Gaucher s disease is at step IV...

In this chapter we will examine how cells and enzymes are used in the transformation of lipids. The lipids are, of course, a very diverse and complex series of molecular entities including fatty acids, triglycerides, phospholipids, glycolipids, aliphatic alcohols, waxes, terpenes and steroids. It is usual to teach about these molecules, in a biochemical context, in more or less the order given above, since this represents a logical sequence leading from simple molecules to the more complex. Here, however, we have adopted a different strategy. 

The presence and biological importance of oligosaccharide structures, usually as components of glycolipids and glycoproteins, in bacterial capsular and cell-wall polysaccharides, in mammalian cell membranes, in cytoplasm, and in extracellular fluids, are now well documented. They are important constituents in... 

Several methylated sugars have been identified in hydrolyzates of LPS, cell-wall polysaccharides, and extracellular polysaccharides. A considerable number of these have been found in the LPS from photosynthetic prokaryotes. Two polysaccharides from Mycobacterium species, a glucan" and a mannan" are remarkable in that they contain high percentages of methylated sugars. Glycolipids from Mycobacterium species are also rich in methylated sugars, some of which have not been found elsewhere, but this is beyond the scope of the present article. 

GLYCOLIPIDS (GLYCOSPHINGOLIPIDS) ARE IMPORTANT IN NERVE TISSUES IN THE CELL MEMBRANE... 

Glycolipids are widely distributed in every tissue of the body, particularly in nervous tissue such as brain. They occur particularly in the outer leaflet of the plasma membrane, where they contribute to cell surface carbohydrates. 

The cell walls of mycobacteria contain three structures peptidoglycan, an arabinogalactan polysaccharide and long chain hydroxy fatty acids (mycolic acids) which are all covalently linked. Additional non-covalently attached lipid components found in the wall include glycolipids, various phospholipids and waxes. The lipid-rich nature of the mycobacterial wall is responsible for the characteristic acid-fastness on staining and serves as a penetration barrier to many antibiotics. Isoniazid and ethambutol have long been known as specific antimycobacterial agents but their mechanisms of action have only recently become more clearly understood. 

Whole-Cell FTMS Glyceride, Phospholipid, and Glycolipid Elucidation... 

The low molecular weight mJz region of spectra derived from microorganism whole cells is generally comprised of mass spectral peaks derived from glycerides, phospholipids, glycolipids, and small protein fragments. This mass spectral information should be examined as a compliment to protein bio-... 

The plasma membrane contains a small amount of carbohydrate (2 to 10% of the mass of the membrane) on the outer surface. This carbohydrate is found attached to most of the protein molecules, forming glycoproteins, and to some of the phospholipid molecules (<10%), forming glycolipids. Consequently, the external surface of the cell has a carbohydrate coat, or glycocalyx. 

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