Chemie und Biochemie der Glykosphingolipoide

Abstract

Glycosphingolipids are naturally occuring substances containing a covalent bound carbohydrate and lipid moiety. In recent years the glycosphingolipid structure, metabolism and biosynthesis have been largely clarified. The biosynthesis has been reported to proceed by stepwise addition of monosaccharide units from sugar nucleotides to glycolipid acceptors with a remarkable specificity of the corresponding enzyme system. Many problems concerning the receptor function, the metabolic and regulatory activity are still to be clarified. There are probably quite different functions for the neutral glycolipids and the acidic, neuraminic acid containing glycolipids, the gangliosides. The latter were thought to be specific components of the brain where they are localized primarily in the neuronal membranes. They are present in normal brain as a mixture of various molecular types. In some lipoidoses a ganglioside accumulation in brain is due to a deficiency of a specific catabolic enzyme.
It is now obvious that gangliosides also occur in low concentration in many extraneuronal animal tissues. In recent studies it could be demonstrated that there are qualitative and quantitative alterations in neutral glycolipid and in ganglioside composition of tumor cells and cells, which have been transformed by viruses. These cells show altered immunological and physical surface properties.