Incorporation of radiolabelled sugars into synaptic junctional macromolecules from chick brain

Individual radiolabelled sugars ([1-14C]-L-fucose, [U-14C]-D-galactose, [U-14C]-D-mannose, [U-14C]-D-glucose and [U-14C]-D-glucosamine) were injected intraventricularly into the forebrains of day-old chickens, and the relative incorporation, after 6 hr, into the glycoprotein sugars, aglycosyl protein, glycolipid sugars and aglycosyl lipid assessed. In addition, the relative total and specific activities of the individual glycoprotein sugars was also determined. Exclusive labelling of glycoprotein sugars (and of the fucose within these oligosaccharides) using fucose as precursor was confirmed, while optimal labelling of glycolipid sugars was achieved using the precursor mannose. Galactose, mannose, glucose and glucosamine were converted to varying degrees to other sugars and non-sugar precursors prior to incorporation. Glucosamine gave rise to the most even distribution of radioactivity among the glycoprotein sugar residues. The highest relative specific activities of the glycoprotein oligosaccharides were achieved using fucose and glucosamine as precursors.