Cerebrosides glucosylceramide

Fig. 10.4. General molecular structure of ceramide and cerebroside (glucosylceramide).

The glycosphingolipids (GSLs) are sugar-containing lipids built on a backbone of ceramide they include galactosyl- and glucosylceramide (cerebrosides) and the gangliosides. Their structures are described in Chapter 14. They are mainly located in the plasma membranes of cells. 

Considerable proportions of cerebroside have been detected in the starfish Asterias rubens.9Ail0 It is a glucosylceramide having a-hydroxy fatty acids (from C16 to C26) and dihydroxy bases whose major components are Cl8 and C22 bases, with one, or two, double bonds. 

The most common cerebrosides include galactosylceramide, glucosylceramide, and sulfatides (see Figure 19.14 for synthesis scheme). Sulfatides are made by transferring a sulfate group to a galactosylceramide (Figure 19.14). 

Glucosylceramide is known to be the precursor of all the major classes of glycosphingolipids in mammalian tissues, while its counterpart, galactosyl-ceramide (GL-lb or cerebroside) gives rise only to a small group of glycolipids. The metabolism of galactosylceramide is discussed later. 

Figure 12.11. Imaging-mode MALDI-IM-MS of a thin tissue section (16 rm) of a rat brain, (a) Structures of glucosylceramide and galactosylceramide, the two major classes of cerebroside molecules. Both cerebrosides are glycosphingolipids, which are impmlant components in nerve cell membranes, (b) Integrated mass spectrum obtained at the specific IM-ATD for these cerebrosides directly from rat brain tissue, (c) False color image of signal intensity for where these cerebrosides occur spatially in the context of the thin tissue section. Imaging MALDI-IM-MS was perfimned at 349 nm using a 2-nm Au nanoparticle matrix, with an imaging spatial resolution of 200 pm.

Renierosides A1-A5 and B1-B3 are a recent series of cerebrosides from an unidentified spedes of the genus Haliclona (= Reniera) harvested in Korea (Ulleung Island). These eight new p-glucosylceramides are characterized by long-chain fatty acids (22-26 carbon atoms) associated with the same tri-unsaturated aminoalcohol. None of them has cytotoxic activity (Mansoor et al, 2007). 

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