Title :
Carbohydrate structures of
beta-trace protein from human cerebrospinal fluid: evidence for "brain-type" N-glycosylation
Abstract :
- The carbohydrate structures of beta-trace protein from human cerebrospinal fluid have been elucidated
- This protein carries exclusively N-linked oligosaccharides at two sites ( Asn29 and Asn56 )
- Enzymatically released N-glycans were studied by com position al and methylation analyses, high-pH anion-exchange chromatography, and liquid secondary ion mass spectrometry
- All glycans were found to be of the complex type , and most (90%) of them were biantennary with no (40%), one (40%), or two (20%) N-acetylneuraminic acid residues
- The rest were triantennary chains or biantennary chains with intact or truncated lactosamine repeats.
- The innermost N-acetylglucosamine residues of nearly all structures were found to be alpha 1,6-fucosylated
- Peripheral fucose (about 20% alpha 1,3-linked to N-acetylglucosamine) was also detected
- Seventy percent of the oligosaccharides contained a bisecting N-acetylglucosamine.
- Especially in the neutral, but also in the monosialylated oligosaccharide fractions, many incomplete antennae consisting of N-acetylglucosamine only were present
- At least 20 different N-glycans were identified
- Analysis of the site-specific glycosylation patterns at Asn29 and Asn56 revealed only minor differences
- According to the structural features (a high degree of fucosylation , high amounts of bisecting N-acetylglucosamine, as well as terminal N-acetylglucosamine and galactose residues , and significant amounts of N-acetylneuraminic acid in alpha 2,3 linkage), this protein can be classified as "brain-type" glycosylated