Title : Characterization of
the oligosaccharide side chain of
apolipoprotein C-III from human plasma very low density
lipoproteins
Abstract :
- 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