Ceramide-based sphingolipids

Inositolphosphoryl ceramide-type sphingolipids were isolated from hyphal forms of C. albicans and three classes of molecules were fractionated by preparative HPLC on silica gel [65], Molecular species in each class differ in the composition of long chain bases and fatty acids the most abundant long chain bases were Cl8 and C20 phytosphingosines, while hydroxy and non-hydroxy C24, C25 and C26 were the most abundant fatty acids. The proposed structures, Ins-P-Cer, Man-Ins- P-Cer and Ins-P-Man-Ins-P-Cer, closely resemble the sphingolipids identified in S. cerevisiae [53],... 

Figure 12.12 Sphingomyelins. Sphingomyelins are esters of a ceramide and phospho-ryl choline. However, similar compounds are ceramide-1-phosphoryl ethanolamines and phosphono forms of sphingolipids. Ceramides W-acyl-sphingosines) are amides of a long chain di- or trihydroxy base containing 12 to 22 carbon atoms, of which sphingosine (4-sphingenine) is the commonest, and a long chain fatty acid whose acyl chain is shown by R1. This may contain up to 26 carbon atoms.

The chemical structure of fumonisin (Fig. 5.IB) is remarkably similar to that of the sphingoid bases sphinganine (Sa) and sphingosine (So), and fumonisin has been shown to inhibit the enzyme ceramide synthase in de novo sphingolipid metabolism (Wang et al., 1991). Ceramide synthase... 

Figure 1.6. Typical structures of sphingolipids (phosphosphingolipid and glycosphingolipid classes), based on a dl8 l ceramide (R = fatty acid group).

Lipids are made up of many classes of very different molecules that all show solubility properties in organic solvents. Mass spectrometry plays a key role in the biochemistry of lipids. Indeed, mass spectrometry allows not only the detection and determination of the structure of these molecules but also their quantification. For practical reasons, only the fatty acids, acylglycerols and bile acids are discussed here, although other types of lipids such as phospholipids, [253-256] steroids, [257-259] prostaglandins, [260] ceramides, [261,262] sphingolipids [263,264] and leukotrienes [265,266] have been analysed successfully by mass spectrometry. Moreover, the described methods will be limited to those that are based only on mass spectrometry, even if the majority of these methods generally are coupled directly or indirectly with separation techniques such as GC or HPLC. A book on the mass spectrometry of lipids was published in 1993. [267]... 

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