Our research has been based on the biosynthetic pathway to <i>N</i>-linked glycoproteins, species which are comprised of an oligosaccharide moiety attached to the side-chain nitrogen atom of an asparagines residue in a peptide. In order to effectively study the steps involved in the biosynthesis of lipid-linked oligosaccharides and their subsequent transfer to a nascent protein in cotranslational modification processes, it is essential to have a source of pure dolichols in quantities sufficient to allow the synthesis of both biosynthetic intermediates and synthetic analogues in the pathways responsible for the biogenesis of glycoproteins. Since supplies of naturally occurring dolichols are scarce and they are difficult to synthesise, a number of lipid substrates were prepared as synthetic analogues of naturally occurring dolichyl phosphate. (Fig. 6302A) The synthesis and biological testing of lipids 1 and 2 are reported. The result of a study of the fluorescence of lipid 1 is also presented. Work towards the preparation of lipid 3 is detailed. Many of the enzymes involved in the biosynthesis of <i>N-</i>linked glycoproteins have already been isolated and characterised, however, some of those enzymes involved in the early stages of <i>N</i>-glycan biosynthesis remain unidentified. In order to gain more information about the unknown mannosyltransferases that are active in the early stages of <i>N</i>-glycan biosynthesis, a phytanyl-linked monosaccharide (glucosamine), 4, and disaccharide (chitobiose), 5, were prepared. (Fig. 6302B) The syntheses of chitobiose phosphate from commercially available chitobiose octaacetate is reported. Details of the preparation of <i>N</i>-acetyl glucosaminyl phosphate from commercially available <i>N</i>-acetyl glucosamine are pretend. The lipid moiety, phytanyl phosphate, was derived from commercially available phytol. The manner in which phytanyl phosphate was coupled to both the monosaccharide phosphate and the disaccharide phosphoryl species is detailed and results of subsequent biological testing are reported. Finally, work towards the preparation of a fluorescently-labelled asparagine-linked chitobiosyl substrate, 6, is reported.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:651864 |
| Date | January 2004 |
| Creators | Guilly, Selena |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/16997 |
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