OCCURRENCE OF ALPHA-1-2-FUCOSYLATION IN MEMBRANE-GLYCOPROTEINS OF MORRIS HEPATOMA 7777 BUT NOT IN LIVER - ABERRANT TYPE OF FUCOSYLATION IN A MALIGNANT-TISSUE

A comparative study was undertaken to characterize the linkages Of L-fucose in N-glycans of plasma membrane glycoproteins from Morris hepatoma 7777, host liver and kidney cortex, as well as from rat serum. After in-vivo radiolabelling of rats with L-[6-H-3]fucose, the asparagine-linked carbohydrate chains were released from delipidated plasma membrane glycoproteins, as well as from serum glycoproteins, by enzymic digestion with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase from Flavobacterium meningosepticum. They were then converted to their corresponding oligosaccharide alditols by reduction with sodium borohydride. Two specific alpha-L-fucosidases from almond emulsin and from Aspergillus niger, combined with affinity HPLC on immobilized Aleuria aurantia lectin were used to study the linkage Of L-fucose in the oligosaccharide chains. Fucose alpha1-2 linked to galactose, was present only in the plasma membrane of hepatoma 7777 (18% of total L-[H-3]fucose in N-glycans), but was not expressed in host liver, kidney cortex and serum. None of the investigated sources contained an appreciable amount of fucose alpha1-3/4 linked to N-acetyl-D-glucosamine. All the radioactively labelled oligosaccharides from host liver, kidney cortex and serum, but only 82% of these oligosaccharides from hepatoma, contained alpha-fucosyl residues linked at the C6 position of the proximal N-acetyl-D-glucosamine.