Title : Structure of the
N- and O-glycans of the
A-chain of human plasma
alpha 2HS-glycoprotein as deduced from the chemical com
positions of the derivatives prepared by stepwise degradation with exoglycosidases
Abstract :
- The structure of the glycans of the A-chain of human plasma alpha 2HS-glycoprotein was established from the chemical com positions of its derivatives prepared by sequential enzymatic degradation of the carbohydrate moiety , from the determination of the kind and amount of the monosaccharides liberated after each step of the enzymatic digestion, and from the distinct specificity of the highly purified exoglycosidases
- The exoglycosidases were three sialidases (Vibrio cholerae, fowl plague virus, and Arthrobacter ureafaciens), two beta-galactosidases (Streptococcus pneumoniae and bovine testis), one alpha-N-acetylgalactosaminidase , one beta-N-acetylglucosaminidase , and one alpha-mannosidase
- Utilizing sialidases with different cleavage specificities, the number of alpha 2-3- and alpha 2-6-linked sialic acid residues could be separately determined
- As to the beta-galactosidases, the enzyme isolated from S. pneumoniae cleaves only beta 1-4-linked galactose residues, whereas the bovine testes enzyme acts on both the beta 1-4- and beta 1-3-linked galactose residues.
- Jack bean beta-N-acetylglucosaminidase cleaves beta 1-2, beta 1-4, and beta 1-6 GlcNAc with higher activity for the beta 1-2
- Jack bean alpha-mannosidase cleaves alpha 1-2, alpha 1-6, and alpha 1-3 Man with greater activity for alpha 1-2 and alpha 1-6
- Bovine liver alpha-N-acetylgalactosaminidase cleaves O-linked GalNAc.
- On the basis of these results, the A-chain of alpha 2 HS-glycoprotein was found to possess two biantennary N-glycans and two O-linked trisaccharides.