Ceramide attachments

Glycohpids (5,14) are primarily glycosphingoHpids, molecules that have oligosaccharide groups attached to ceramide [104404-17-3]. They are present, at least in small amounts, in the membranes of most, if not all, tissues. They too, like cell-membrane glycoproteins, are recognition deterrninants. 

Figure 11.24 A summary of the reactions involved in synthesis of sphingomyelin. Reaction between serine and palmitoyl-CoA produces 3-oxosphinganine, which is converted to sphingamine. Attachment of a Long-chain fatty acid to the amino group of sphinganine produces dihydroxyceramide. Ceramide reacts with phosphatidylcholine the phosphocholine component forms an ester bond with the hydroxyl group at position one of ceramide.

Attachment of another long-chain fatty acid in an amide linkage to the amino group of sphingosine forms a ceramide, the parent compound for many of the physiologically important sphingolipids. 

Scheme 1. The Attachment of Different Monosaccharides to the Ceramide (Cer) Moiety.

The glycosphingolipids differ from sphingomyelin in that they do nflt contain phosphate, and the polar head function is provided by a monosaccharide or oligosaccharide attached directly to the ceramide by... 

Structural components and function of sphingomyelin The alcohol sphingosine attached to a long-chain fatty acid produces a ceramide. Addition of a phosphorylcholine produces the phospholipid sphingomyelin, which is the only significant sphingophospholipid in humans. It is an important constituent of myelin. 

As the final outer stratum comeum is formed the phospholipid bilayer deteriorates and intercellular lipid layers are formed.k l These contain principally ceramides, cholesterol, and free fatty acids. Some sphingolipids are covalently attached to proteins.3... 

Ogawa and co-workers [97] have synthesised the complete glycosphingolipid (361) containing the terminal tetrasaccharide (356) of the Leb antigen attached to lactosyl ceramide. The lactose derivative (95), prepared by the action of trimethylamine — borane and aluminium chloride [99] on the benzylidene derivative (94), was condensed with the thioglucoside (362) in the presence of methyl triflate and molecular sieve to give the trisaccharide (363). This was deacetylated and the product (364) condensed... 

---