Studies on the Hydrazinolysis of Glycoproteins

Hydrazinolysis of porcine thyroglobulin glycopeptides and of pineapple stem bromelain EC 3.4.22.4 permitted the isolation of almost intact carbohydrate chains of these glycoproteins. On the basis of permethylation analyses of the released oligosaccharides after reduction with NaBH4, the core structures of Unit A-type and Unit B-type carbohydrate chains of porcine thyroglobulin were deduced to be Manalpha1 leads to 6Manalpha1 leads to 3Manbeta1 leads to 4GlcNAcbeta1 leads to 4Ralpha1 leads to 6GlcNAc leads to Asn (Unit A-type, R=H; Unit B-type, R=Fuc), and that of bromelain was found to be Manalpha1 leads to 6R'1 leads to 2Manbeta1 leads to 4GlcNAcbeta1 leads to 4R1 leads to 3GlcNAc leads to Asn (R'=Xylbeta and R=Fucalpha, or R'=Fucalpha and R=Xylbeta). From these results, it appears that the hydrazinolysis method is applicable to wide variety of glycoproteins which have an N-glycosylamine linkage between the carbohydrate and peptide moieties, regardless of the type of linkage to the most proximal N-acetylglucosamine residue which is bound to asparagine.