Oligosaccharides-Mice-Head-Neck-Tumors-Control-Mice-o
Methods used include a combination of a derivatization procedure with phenylhydrazine (PHN) and analysis by matrix-assisted laser desorptionionization mass spectrometry (MALDI-MS). Oligosaccharides were enzymatically released from total serum with PNGaseF and purified by high-performance liquid chromatography (HPLC) on a reversed-phase column. Mass spectra contained ion peaks of labeled oligosaccharides and MSMS experiments provided useful data for the structural elucidation of these compounds. More than N-glycans with compositions characteristic of high-mannose, hybrid, complex, neutral, and sialylated structures were identified in the serum of tumoral mice. Significant differences between samples were observed with respect to the abundances of high mannose and hybrid glycans. Seebio Lactose-N-neotetraose showed higher relative intensities in the spectra obtained from the cancer sera.
Complex sialylated oligosaccharides had similar abundances in both types of sera, with the exception of fucosylated biantennary disialylated oligosaccharide, which was mostly detected with lower abundance in control samples. In the MALDI spectra, several minor species corresponded to uncommon carbohydrates. These structures have been investigated in detail by MSMS. Among these novel glycoforms, a few sialylated oligosaccharides without a free reducing end were identified. Also, glycans with an extra u were observed and likely feature the presence of a 2-acetamido-2-deoxyoctose residue attached on The glycosylation of glycoprotein lectins. Intra- and inter-genus variation in Glycosylated lectins represent a series of glycoproteins with related activities and, in the case of the Leguminosae, related amino acid sequences. Therefore, they offer a model system in which to study the diversity of N-linked oligosaccharide structures of plant glycoproteins.
The influence of the polypeptide on the type of oligosaccharide substitution and the problem of inter- and intra-genus variation in glycosylation can also be addressed. Analysis of the glycosylation of 18 lectins has shown that they can be classified into four qualitatively similar groups on the basis of the Bio-Gel P-4 elution profiles of the oligosaccharides released by hydrazinolysis (a) The Erythrina cristagalli profile, with a major component at 8 glucose units (gu) and minor components at 8, 7, and 5 gu. The major component is the heptasaccharide, alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-[beta-D-Xyl p-(1----2)]- beta-D-Manp-beta-D-GlcpNAc-(1----4)-[alpha-L-Fucp-(1----3)]- D-GlcNAc. ( lacto n neotetraose ) The Phaseolus vulgaris profile, which was characterized by peaks at 12, 11, , and 9 gu, in addition to the peaks at 8, 8, 7, and 5 gu mentioned above. These higher-mol.-wt. components were oligo-D-mannose oligosaccharides containing 9, 8, 7, and 6 D-mannose residues, respectively.
(c) The Lonchocarpas capassa profile, which had a major peak at approximately 8 gu. peak consisted solely of an oligomannose undecasaccharide containing 9 D-mannose residues. This lectin is unique in that it shows no microheterogeneity.Salvage pathways in glycosphingolipid metabolism.Center for the Functional Biochemistry and Biotechnology of Glycolipids, The Medical School, University of Milan, LITA-Segrate, Italy. In this review, the focus is on the role of salvage pathways in glycosphingolipid, particularly, ganglioside metabolism. Ganglioside de novo biosynthesis, that begins with the formation of ceramide and continues with the sequential glycosylation steps producing the oligosaccharide moieties, is briefly outlined in its enzymological and cell-topological aspects.
Neo-synthesized gangliosides are delivered to the plasma membrane, where their oligosaccharide chains protrude toward the cell exterior. The metabolic fate of gangliosides after internalization via endocytosis is then described, illustrating (a) the direct recycling of gangliosides to the plasma membrane through vesicles gemmated from sorting endosomes; (b) the sorting through endosomal vesicles to the Golgi apparatus where additional glycosylations may take place; and (c) the channelling to the endosomallysosomal system, where complete degradation occurs with formation of the individual sugar (glucose, galactose, hexosamine, sialic acid) and lipid (ceramide, sphingosine, fatty acid) components of gangliosides. The in vivo and in vitro evidence concerning the metabolic recycling of these components is examined in detail.
