The biosynthesis of glycolipids during the differentiation of the slime mold dictyostelium discoideum

Abstract

In the slime mold Dictyostelium discoideum polysioprenylphosphomannosides are substrates for membrane bound mannosyltransferases; the isolated and purified isoprenyl derivatives transfer mannose to protein in vitro in presence of membrane fractions. The biosynthesis of the mannolipids as well as the biosynthesis of a glucose containing cerebroside, which becomes synthesized in an early stage of the cell development proceeds under control of the cell differentiation. The isolation procedure and the properties of the glycolipids are described, and their functions for the cellular development are discussed.

Modifications of lysosomal enzymes in Dictyostelium discoideum

“…In Dictyostelium, the N-linked oligosaccharides are composed of residues of GlcNAc, Man, and Fuc (39). Phosphoryl dolichol-like derivatives of Man and Glc have been described and are thought to act as intermediates in the biosynthesis of the Nqinked oligosaccharides (26)(27)(28). Protein glycosylation occurs cotranslationally by enbloc transfer of a Glc3Man9GlcNAc2 oligosaccharide from a dolichol-like lipid precursor similar to that described for many eukaryotic systems (1,2).…”

“…Most of the available information about the glycoconjugates of Dictyostelium is confined to glycoproteins. Limited studies have also been done on glycolipids (26)(27)(28)(29) and on the complex glycans of the surface sheath and the structural components of the stalk and spore cells (30)(31)(32)(33)(34)(35)(36). The current discussion will focus on glycoproteins with Nlinked oligosaccharides, but it should be emphasized that the composition, structure, and the function of the extracellular matrices is nearly completely unknown.…”

The dependence of glycosyltransferases inDictyostelium discoideum on the structure of polyisoprenols

“…But rather it could be shown an increasing incorporation of mannose into lipids. These glycolipids were isolated by the extraction described earlier (1). Under these conditions the mannolipid formed by the endogenous polyisoprenol becomes coextracted together with those synthesized by the exogenous polyisoprenylphosphates.…”

Products of endogenous N-acetylglucosaminyltransferase activity of Dictyostelium discoideum during growth and early development

“…Although these observations are clearly suggestive of the involvement of glycosubstances in the developmental process, little information is currently available regarding the biosynthesis of glycosubstances in D. discoideum during growth and early development. Quantitative changes in the levels of various glycosyltransferase activities during D. discoideum development have been reported (18,20), but the significance of these results is difficult to determine since the assays rely on sugar transfer to a limited concentration of endogenous acceptors (17).…”