Novel oligosaccharide chains on polysialoglycoproteins isolated from rainbow trout eggs. A unique carbohydrate sequence with a sialidase-resistant sialyl group, DGalNAc.beta.1 .fwdarw. 4(NeuGc2 .fwdarw. 3)DGalNAc

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Abstract
A series of novel carbohydrate chains all possessing a hitherto unknown trisaccharide unit, GalNAc.beta.1 .fwdarw. 4-(NeuGc2 .fwdarw. 3)GalNAc.beta.1 .fwdarw., were isolated from trout egg polysialoglycoproteins, a new class of glycoproteins, on alkali-borohydride treatment. On the basis of chemical (methylation, Smith degradation and hydrazinolysis-nitrous deamination) and direct-probe mass spectrometric methods, the structures of a series of the 1st major type of oligosaccharide alditols having a sialidase-resistant N-glycolylneuraminic acid residue in each molecule were determined. The structures thus determined are novel and all possess a unique carbohydrate sequence (sialidase-resistant unsubstituted sialyl group italicized): GalNAc.beta.1 .fwdarw. 4(NeuGc2 .fwdarw. 3)GalNAc.beta.1 .fwdarw. 3Gal.beta.1 .fwdarw. -4Gal.beta.1 .fwdarw.3 [(.fwdarw. 8NeuGc.alpha.2)n .fwdarw. 6)GalNAcol (n = 0 through 3).