title: Structure determination by MALDI-IRMPD mass spectrometry and exoglycosidase digestions of O-linked oligosaccharides from Xenopus borealis egg jelly.
abstract: Differences in the fertilization behavior of Xenopus borealis from X. laevis and X. tropicalis suggest differences in the glycosylation of the egg jellies. To test this assumption, O-linked glycans were chemically released from the egg jelly coat glycoproteins of X. borealis. Over 50 major neutral glycans were observed, and no anionic glycans were detected from the released O-glycan pool. Preliminary structures of ∼30 neutral oligosaccharides were determined using matrix-assisted laser desorption/ionization (MALDI) infrared multiphoton dissociation tandem mass spectrometry (MS). The mass fingerprint of a group of peaks for the core-2 structure of O-glycans was conserved in the tandem mass spectra and was instrumental in rapid and efficient structure determination. Among the 29 O-glycans, 22 glycans contain the typical core-2 structure, 3 glycans have the core-1 structure and 2 glycans contained a previously unobserved core structure with hexose at the reducing end. There were seven pairs of structural isomers observed in the major O-linked oligosaccharides. To further elucidate the structures of a dozen O-linked glycans, specific and targeted exoglycosidase digestions were carried out and the products were monitored with MALDI-MS. Reported here are the elucidated structures of O-linked oligosaccharides from glycoproteins of X. borealis egg jelly coats. The structural differences in O-glycans from jelly coats of X. borealis and its close relatives may provide a better understanding of the structure-function relationships and the role of glycans in the fertilization process within Xenopodinae.
authors.affiliation: Department of Chemistry, Biochemistry and Molecular Medicine, University of California, Davis, USA.
authors.forename: Bensheng
authors.initials: B
authors.lastname: Li
authors.forename: Scott C
authors.initials: SC
authors.lastname: Russell
authors.forename: Jinhua
authors.initials: J
authors.lastname: Zhang
authors.forename: Jerry L
authors.initials: JL
authors.lastname: Hedrick
authors.forename: Carlito B
authors.initials: CB
authors.lastname: Lebrilla
mesh_terms: D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006026:Glycoside Hydrolases / Q000378:metabolism*; D006031:Glycosylation; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry* / Q000378:metabolism; D010063:Ovum / Q000737:chemistry*; D010802:Phylogeny; D011134:Polysaccharides / Q000737:chemistry* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014981:Xenopus / Q000254:growth & development / Q000378:metabolism*
chemical_list: D009844:Oligosaccharides; D011134:Polysaccharides; D006026:Glycoside Hydrolases