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Redefined substrate specificity of ST6GalNAc II: a second candidate sialyl-Tn synthase
1Molecular Glycobiology, Frontier Research Program, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama, Japan.
Biochemical and Biophysical Research Communications
|June 29, 2000
Summary
Both ST6GalNAc I and II enzymes can synthesize sialyl-Tn antigens, challenging previous assumptions. This finding expands our understanding of O-linked oligosaccharide synthesis and identifies new candidates for sialyl-Tn synthases.
Area of Science:
- Biochemistry
- Glycobiology
- Enzymology
Background:
- O-linked oligosaccharides are crucial in biological processes.
- ST6GalNAc I and II are enzymes involved in O-linked oligosaccharide synthesis.
- Previous studies suggested only ST6GalNAc I synthesizes sialyl-Tn antigen.
Purpose of the Study:
- To reexamine the acceptor substrate specificities of ST6GalNAc I and II.
- To investigate the role of ST6GalNAc II in sialyl-Tn antigen synthesis.
- To clarify the enzymatic pathways of O-linked oligosaccharide biosynthesis.
Main Methods:
- Enzyme activity assays using ovine submaxillary mucin (OSM) and a synthetic polymer [Ala-Thr(GalNAc)-Ala]n.
- Comparison of ST6GalNAc I and II activity on specific substrates.
- Analysis of carbohydrate structures synthesized by the enzymes.
Main Results:
- Both ST6GalNAc I and ST6GalNAc II exhibited activity toward asialo-ovine submaxillary mucin.
- Both enzymes showed activity on the [Ala-Thr(GalNAc)-Ala]n polymer, which contains GalNAc-O-Thr/Ser structures.
- Evidence suggests ST6GalNAc II can also synthesize sialyl-Tn antigen structures.
Conclusions:
- ST6GalNAc I and ST6GalNAc II are both capable of synthesizing sialyl-Tn antigen.
- The previous assertion that only ST6GalNAc I synthesizes this structure is revised.
- Both enzymes are potential candidates for sialyl-Tn synthases in O-linked oligosaccharide synthesis.