The glycolipids are a
structurally heterogeneous group of membrane components found in organisms
ranging from bacteria to man. To simplify the classification task, we have
enlarged the previous definition given in 1970 by IUPAC-IUB (Commission on
Biochemical Nomenclature), "any compound containing a
carbohydrate group linked by glycosyl linkage to a lipid moiety", in
ignoring the type of linkage between the two basic constituents.
A revised nomenclature of the main glycolipids is found in the recommendations released by the International Union of Pure and Applied Chemistry (IUPAC) in 1997 (Pure Appl Chem 1997, 69, 2475 and web site).
This class of lipids includes various types of long chain derivatives of sugars which may contain most frequently in bacteria and plants a glycerol (a diacylglycerol) backbone and in animals a ceramide backbone. A sterol or a phosphorylated polysaccharide-lipid complex may be also found. Some simple glycolipids may also be composed of a carbohydrate moiety linked to a single fatty acid or fatty alcohol.
A great variety of glycolipids is also found in bacteria where specific glycopeptidolipids or lipopolysaccharides are also present. The most important molecules will be described here.
According to their structure, glycolipids may be classified into the following groups:
1 - Glycolipids based on glycerol
2 - Glycolipids based on ceramides
3 - Lipopolysaccharides
4 - Glycosides of sterols
5 - Glycosides of fatty acids, alcohols or amino alcohols
6 - Glycopeptidolipids (glycosylated fatty acylated peptides)