Title : Identification and determination of absolute and anomeric configurations of
the 6-deoxyaltrose residue found in
polysialoglycoprotein of Salvelinus leucomaenis pluvius eggs
Abstract :
- The first demonstration of the presence of a 6-deoxyhexose other than fucose in glycoprotein
- An oligosaccharide alditol, dHex-GalNAc-Gal-Gal-GalNAcol, has been isolated from polysialoglycoprotein , which was derived from the unfertilized eggs of Savelinus leucomaenis pluvius (a salmonid fish, Iwana in Japanese), by alkaline borohydride treatment followed by exhaustive digestion with sialidase
- First, the structure of the terminal dHex residue in the above pentasaccharide residue in the above pentasaccharide has been assigned as 6-deoxyaltrose (= dAlt in pyranoid form) by a combination of structural methods ( GLC, TLC , mass spectrometry, and 400-MHz 1H-NMR spectroscopy)
- The occurrence of a 6-deoxyhexose other than L-fucose in glycoprotein has not been previously reported
- Next, the absolute configuration of this unusual sugar residue has been assigned as D on the basis of the exciton-splitting study of tris-p-bromobenzoate derivatives of methyl 6-deoxyaltrosides
- The usefullness of this circular dichroic exciton-splitting method in the determination of the absolute configuration of carbohydrate components , only available in minute amounts, is emphasized
- The anomeric configuration of the glycosidic linkage of the D-altropyranosyl residue was deduced from 400-MHz 1H NMR spectroscopy
- The 6-deoxy-beta-D-altropyranosyl residue thus established has the same configuration as alpha-L-fucose but with the C-5 methyl group inverted, suggesting that the biosynthetic incorporation of D-dAlt parallels that of L-fucose, and a possible pathway is also considered