Frequent occurrence of pre-existing alpha 2-->8-linked disialic and oligosialic acids with chain lengths up to 7 Sia residues in mammalian brain glycoproteins. Prevalence revealed by highly sensitive chemical methods and anti-di-, oligo-, and poly-Sia antibodies specific for defined chain lengths.
The pre-existence of alpha2-->8-linked disialic acid (di-Sia) and oligosialic acid (oligo-Sia) structures with up to 7 Sia residues was shown to occur on a large number of brain glycoproteins, including neural cell adhesion molecules (N-CAMs), by two highly sensitive chemical methods (Sato, C., Inoue, S., Matsuda, T., and Kitajima, K. (1998) Anal. Biochem. 261, 191-197; Sato, C., Inoue, S., Matsuda, T., and Kitajima, K. (1999) Anal. Biochem. 266, 102-109). This unexpected finding was also confirmed using a newly developed antibody prepared using a copolymer of alpha2-->8-linked N-acetylneuraminyl p-vinylbenzylamide and acrylamide as an immunogen and known antibodies whose immunospecificities were determined to be di- and oligo-Sia residues with defined chain lengths. The major significance of the new finding that di- and oligo-Sia chains exist on a large number of brain glycoproteins is 2-fold. First, it reveals a surprising diversity in the number and M(r) of proteins distinct from N-CAM that are covalently modified by these short sialyl glycotopes. Second, it suggests that synthesis of di- and/or oligo-Sia units may be catalyzed by alpha2-->8-sialyltransferase(s) that are distinct from the known polysialyltransferases, STX and PST, which are partially responsible for polysialylation of N-CAM.
Sato
C
C
Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
Fukuoka
H
H
Ohta
K
K
Matsuda
T
T
Koshino
R
R
Kobayashi
K
K
Troy
F A
FA
Kitajima
K
K
D000818:Animals; D000911:Antibodies, Monoclonal; D001923:Brain Chemistry; D004187:Disaccharides / Q000032:analysis* / Q000737:chemistry; D004622:Embryo, Mammalian; D006023:Glycoproteins / Q000737:chemistry*; D006168:Guinea Pigs; D019006:Neural Cell Adhesion Molecules / Q000737:chemistry; D009844:Oligosaccharides / Q000032:analysis* / Q000737:chemistry; D012794:Sialic Acids / Q000032:analysis*; D013552:Swine
D000911:Antibodies, Monoclonal; D004187:Disaccharides; D006023:Glycoproteins; D019006:Neural Cell Adhesion Molecules; D009844:Oligosaccharides; D012794:Sialic Acids