Characterization of the oligosaccharide side chain of apolipoprotein C-III from human plasma very low density lipoproteins.
Apolipoprotein C-III1 and apolipoprotein C-III2 each contain one oligosaccharide side chain, bound O-glycosidically to threonine in position 74 of the amino acid sequence. The studies reported in this paper characterize these alkali labile oligosaccharides, thereby demonstrating the complete structure of apolipoprotein C-III. Monosaccharide analysis revealed the following sugar composition: D-galactose/N-acetyl-D-galactosamine/sialic acid 1 : 1 : 1 and 1 : 1 : 2 for apolipoprotein C-III1 and apolipoprotein C-III2, respectively. Treatment of desialylated apolipoproteins with alkaline borohydride released the reduced disaccharide beta-D-galactosyl-(1 leads to 3)-N-acetyl-D-galactosaminitol, which was detected by gas-liquid chromatography. Further studies employing periodate oxidation and Smith degradation indicated that the structure of the trisaccharide from apolipoprotein C-III1 was alpha-N-acetylneuraminyl-(2 leads to 3)-beta-D-galactosyl-(1 leads to 3)-N-acetyl-D-galactosaminitol. The tetrasaccharide structure from apolipoprotein C-III2 is made up of this trisaccharide plus one sialic acid residue linked to C6 of N-acetyl-D-galactosaminitol, as was shown by the assessment of chromogens formed upon alkaline degradation.
D000468:Alkalies; D001053:Apolipoproteins / Q000097:blood*; D055598:Chemical Phenomena; D002621:Chemistry; D004187:Disaccharides / Q000032:analysis; D006801:Humans; D008079:Lipoproteins, VLDL / Q000097:blood*; D009005:Monosaccharides / Q000032:analysis; D009844:Oligosaccharides / Q000097:blood*; D010084:Oxidation-Reduction
D000468:Alkalies; D001053:Apolipoproteins; D004187:Disaccharides; D008079:Lipoproteins, VLDL; D009005:Monosaccharides; D009844:Oligosaccharides