Structural elucidation of N-linked sugar chains of storage glycoproteins in mature pea (Pisum sativum) seeds by ion-spray tandem mass spectrometry (IS-MS/MS)

The structures of N-linked sugar chains of the storage glycoproteins in mature pea seeds have been estimated. Nine pyridylaminated (PA-) N-linked sugar chains were derived and purified from the hydrazinolysate of the storage glycoproteins by reversed-phase HPLC and size-fractionation HPLC. The structures of the PA-sugar chains purified were first identified by two-dimensional PA-sugar chain mapping, considering the data of sugar composition analysis or sequential exoglycosidase digestions. The deduced structures were further analyzed by IS-MS/MS analysis. Every relevant fragment ion derived from all PA-sugar chains could be assigned on the basis of deduced structures. The estimated nine structures fell into two categories; the first was a typical oligomannose type (Man(8-3)GlcNAc(2); 77.7%) which can be hydrolyzed by endo-beta-N-acetylglucosaminidase PS [Y. Kimura et al., Biosci, Biotech. Biochem., 60, 228-232 (1996)], the second was a xylose-containing type (Man(4-3)Xyl(1)GlcNAc(2), Man(3)Fuc(1)Xyl(1)GlcNAc(2); 22.3%). Among these structures, Man(8)GlcNAc(2) (19.7%), Man(6)GlcNAc(2) (24.7%), and Man(3)Fuc(1)Xyl(1)GlcNAc(2) (18.8%) were the dominant structures.