O-glycan core structures

O-glycan core structures in many cells. The core 1 structure is also called T antigen in pathologic studies. Core 1 fSl,3-galactosyltransferases (core 1 fil,3GalT), which are responsible for the synthesis of core 1 disaccharide, have been purified recently (83, 84). 

FIGURE 7.6 Eight types of O-glycan core structures. (Adapted from Peter-Katahnic, J. Methods Enzymol, 405, 139, 2005. With permission.)... 

Fig. 15.3. Structures of the four most commonly observed O-glycan cores.

T. A. Gerken, Kinetic modeling confirms the biosynthesis of mucin core 1 (/i-Gal (1 -3)x-Gal YAc-O-Ser/Thr) O-glycan structures are modulated by neighboring glycosylation effects, Biochemistry, 43 (2004) 4137—4142. 

Huang, H.H., Tsai, P.L. and Khoo, K.H. (2001) Selective expression of different fucosylated epitopes on two distinct sets of Schistosoma mansoni cercarial O-glycans identification of a novel core type and Fewis X structure. Glycobiology 11, 395 106. 

Fig. 3. O-glycans of the mucin type. A core 2 structure with poly-LacNAc and blood group epitope A B core 4 structure with sialyl Lex epitope. The core structures are written in bold letters...

Core structures of mucin-type O-linked glycans. These represent a series of characteristic structures attached to a serine (S) or threonine (T) amino acid residue of a protein. There are eight core structures, each of which may have further monosaccharide additions. Tn is a precursor of theT (Thomsen-Freidenreich) antigen which is commonly used as a marker for tumor cells. 

Biosynthesis of GPI anchors starts with the core structure assembly by sequential addition of UDP-GlcNAc (followed by iV-deacetylation), dolichol-phosphate-mannose, and phospho-ethanolamine to phosphatidylinositol and culminates in the en bloc transfer to protein shortly after the protein is synthesized. However, the biosynthetic pathways can differ strikingly between different organisms with respect to specific modifications and fatty acid remodeling occurring after completion of the core glycan. This also applies for the point when certain modifications are introduced, e. g. before or after the transfer of the GPI-moiety to the protein. GPI anchors can be cleaved at defined positions by an array of enzymatic and chemical methods, respectively (O Fig. 5). Thus, it becomes possible to identify GPI-anchored proteins and, moreover, analyze the structure and biosynthesis of GPI anchors [103]. 

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