Detailed structural features of glycan chains derived from  1-acid glycoproteins of several different animals: the presence of hypersialylated, O-acetylated sialic acids but not disialyl residues

Abstract

We analyzed carbohydrate chains of human, bovine, sheep, and rat alpha1-acid glycoprotein (AGP) and found that carbohydrate chains of AGP of different animals showed quite distinct variations. Human AGP is a highly negatively charged acidic glycoprotein (pKa = 2.6; isoelectic point = 2.7) with a molecular weight of approximately 37,000 when examined by matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and contains di-, tri-, and tetraantennary carbohydrate chains. Some of the tri- and tetraantennary carbohydrate chains are substituted with a fucose residue (sialyl Lewis x type structure). In sheep AGP, mono- and disialo-diantennary carbohydrate chains were abundant. Tri- and tetrasialo-triantennary carbohydrate chains were also present as minor oligosaccharides, and some of the sialic acid residues were substituted with N-glycolylneuraminic acid. In rat AGP, very complex mixtures of disialo-carbohydrate chains were observed. Complexity of the disialo-oligosaccharides was due to the presence of N, O-acetylneuraminic acids. Triantennary carbohydrate chains carrying N,O-acetylneuraminic acid were also observed as minor component oligosaccharides. We found some novel carbohydrate chains containing both N-acetylneuraminic acid and N-glycolylneuraminic acid in bovine AGP. Interestingly, triantennary carbohydrate chains were hardly detected in bovine AGP, but diantennary carbohydrate chains with tri- or tetrasialyl residues were abundant. Furthermore the major sialic acid in these carbohydrate chains was N-glycolylneuraminic acid. It should be noted that these sialic acids are attached to multiple sites of the core oligosaccharide and are not present as disialyl groups.

Specific Extraction of Sialic-acid-containing Glycans and Glycopeptides Using Serotonin-bonded Silica

“…This glycoprotein consists of biantennary and triantennary glycans with variation in the number of NeuAc and their linkage position in lactosamine branches, and Galβ1→3GlcNAcβ1→4 sequence as well as usual Galβ1→4GlcNAcβ1→4 sequence in Manα1→3 branch. 38 These peaks were disappeared by neuraminidase digestion. Therefore all peaks appeared in Fig.…”

“…42 Each glycosylation site contains highly sialylated bi-, tri-and tetraantennary glycans; some tri-and tetraantennary glycans are fucosylated at one of the lactosamine branch to form a sialyl Lewis-X (sLe x , NeuAcα2→3Galβ1→4(Fucα1→3) GlcNAc-) sequence. 38 Figures 6(a) and 6(c) show TIC and their SIM profiles of the tryptic digests. Many peaks were detected in their chromatograms.…”

“…Asn33 AGP1S [26][27][28][29][30][31][32][33][34][35][36][37][38] Asn33 AGP1S [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Asn72…”

Veterinary Biomarker Discovery: Proteomic Analysis of Acute Phase Proteins

“…During inflammation, increases in plasma concentrations of AGP, as well as many structural modifications including the glycoslyation pattern and the degree of branching and fucosylation of AGP have been reported (Ceceliani et al, 2007). The structure of the glycoprotein AGP has been analyzed in several species including cows, sheep and rats, with the results indicating that the glycosylation pattern of AGP was quite variable (Nakano et al, 2004). Using MALDI-TOF MS, it was determined that in sheep the mono-and disialodiantennary carbohydrate chains of AGP were elevated, while the abundance of triand tetra-sialo triantennary carbohydrate chains were decreased.…”

“…No triantennary carbohydrate chains were detected in bovine AGP, however, elevated abundance of diantennary carbohydrate chains with tri-or tetrasialyl residues were observed. In rats, a complex mixture of disialo carbohydrate chains of N, O-acetylneuraminic acids were detected on AGP (Nakano et al, 2004). The glycosylation pattern of AGP in cats was investigated in animals with feline immunodeficiency virus and feline leukemia virus.…”