Metabolic stability of the fucose in rat transferrin

The metabolic behaviour of the chitobiose core fucose that is a natural constituent of a large proportion of rat transferrin molecules was studied in rats comparatively to that of the polypeptide portion of the glycoprotein by using appropriate labels ([3H]fucose and 125I) and affinity chromatographic techniques (lentil-Sepharose). No evidence was obtained to suggest that this residue is cleaved from the glycan in significant amounts before removal of the entire glycoprotein for catabolism. Similarly, [14C]fucose linked to GlcNAc residues in the antennae of human asialotransferrin was being eliminated in pigeons at the same rate as the polypeptide itself. It is concluded that in spite of transferrin's exposure to the cellular milieu, the fate of its fucose is distinctly different from that of the same in plasma membrane glycoproteins.