Redefined substrate specificity of ST6GalNAc II: a second candidate sialyl-Tn synthase.
The acceptor substrate specificities of ST6GalNAc I and II, which act on the synthesis of O-linked oligosaccharides, were reexamined using ovine submaxillary mucin, [Ala-Thr(GalNAc)-Ala]n polymer (n = 7-11). It has been suggested that only ST6GalNAc I can synthesize carbohydrate structures of sialyl-Tn-antigen; i.e., NeuAc alpha2-6GalNAc-O-Thr/Ser [Kurosawa et al., J. Biol. Chem. 269, 19048-19053 (1994)] based on the result that ST6GalNAc I, not ST6GalNAc II, exhibited activity toward asialoagalacto-fetuin. In this study, we present evidence that both ST6GalNAc I and II exhibit activity toward asialo-OSM (ovine submaxillary mucin) and [Ala-Thr(GalNAc)-Ala]n polymer (n = 7-11) which have only the GalNAc-O-Thr/Ser-structures. These results strongly indicate that not only ST6GalNAc I but also II are candidates for sialyl-Tn synthases.
Kono
M
M
Molecular Glycobiology, Frontier Research Program, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama, Japan.
Tsuda
T
T
Ogata
S
S
Takashima
S
S
Liu
H
H
Hamamoto
T
T
Itzkowitz
S H
SH
Nishimura
S
S
Tsuji
S
S
D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry; D019556:COS Cells; D002240:Carbohydrate Sequence; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry; D011994:Recombinant Proteins / Q000378:metabolism; D012756:Sheep; D012799:Sialyltransferases / Q000378:metabolism*; D013379:Substrate Specificity
D015295:Antigens, Tumor-Associated, Carbohydrate; D009844:Oligosaccharides; D011994:Recombinant Proteins; C055491:sialosyl-Tn antigen; D012799:Sialyltransferases; C088391:galactosyl-1-3-N-acetylgalactosaminyl-specific 2,6-sialyltransferase