In this review, systematic synthesis of the ER type of asparagine linked sugar chains are described. The function of asparagine linked sugar chains in the glycoprotein quality control process has recently attracted attention. To construct the target sugar chains, we employed a convergent and stereoselective manner, using four oligosaccharide components, core trisaccharide having a β-mannoside bond, a linear mannotriose, branched manno-oligosaccharide derivatives, and glucose derivatives. Hexasaccharide acceptor was employed as the common intermediate, and coupling with branched manno-oligosaccharide derivatives such as M5, M4B, or M4C donor afforded high-mannose type glycans, corresponding to undecasaccharide M9, dodecasaccharide M8B and M8C, respectively. Finally, synthesized high mannose type sugar chains and glucose derivatives were combined to glucosylated high mannose type glycans of arbitral structures.
This article deals with cell-surface engineering using bacterial cell wall aiming for the development of new mucosal vaccines. We developed a method for artificial modification of live bacteria. As precursors to be incorporated into bacterial cell wall, muramic acid derivatives with ketone moiety were synthesized. When the synthesized precursor was added to growth media, it was transferred through biosynthetic pathway of the cell wall and the ketone group was displayed on the surface of bacteria. Examples of bacterial surface modifications by this method are described.
Escherichia coli O157 is an emerging cause of foodborne illness. To avoid the severe complications such as the hemolytic uremic syndrome caused by the infection of the bacterium, rapid diagnosis is very important. In this context, development of a rapid and highly sensitive detection method of Shiga toxins (Stxs), which are produced by the bacterium, is desired. Stxs are a family of AB5 bacterial toxins, which bind to cell surface glycosphingolipid Gb3Cer through multivalent binding of five B-subunits. This paper reviews a recent development of the materials that can bind to the bacterial toxins with high affinities, including artificial glycolipids, molecules containing multivalent binding components, and natural glycolipid layers mimicking the cell membrane.
We describe herein the syntheses, applications and advantages of novel functional sugar chain molecular probes “Glycan-methotrexate (MTX) 1”. Towards a quantitative understanding of glycan related biological events, Glycan-MTX having endoplasmic reticulum (ER) types of N-glycan were synthesized. These probes have strong affinity to dihydrofolate reductase (DHFR), thus resulting in Glycan-MTX-DHFR complexes 2 which were available as artificial glycoproteins. Bifunctional glycan-graffted DHFR 3 were also created as novel types of artificial glycoproteins. Since Glycan-MTX and corresponding artificial glycoprotein can be detected readily by MTX-tag, they will be effective for analyses of glycan processing enzymes. In particular, it is important, for comprehensive analyses of ER glycoprotein quality control, that M9GN2-MTX 1b is recognized by folding sensor “UDPGlc: glycoprotein glucosyltrasferase (UGGT)”.