Detailed structural features of glycan chains derived from alpha1-acid glycoproteins of several different animals: the presence of hypersialylated, O-acetylated sialic acids but not disialyl residues.
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.
Nakano
Miyako
M
Faculty of Pharmaceutical Sciences, Kinki University, Kowakae 3-4-1, Higashi-Osaka 577-8502, Japan.
Kakehi
Kazuaki
K
Tsai
Men-Hwei
MH
Lee
Yuan C
YC
D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D013058:Mass Spectrometry; D019158:N-Acetylneuraminic Acid / Q000737:chemistry*; D009438:Neuraminic Acids / Q000737:chemistry*; D009961:Orosomucoid / Q000737:chemistry / Q000235:genetics*; D051381:Rats; D012756:Sheep; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D009438:Neuraminic Acids; D009961:Orosomucoid; C032592:N-glycolylneuraminic acid; D019158:N-Acetylneuraminic Acid