Figure 1 | Scientific Reports

Figure 1

From: Computer-aided engineering of a branching sucrase for the glucodiversification of a tetrasaccharide precursor of S. flexneri antigenic oligosaccharides

Figure 1

(A) Overview of the repeating units of most S. flexneri O-Ags showing the tetrasaccharide backbone ABCD and sites of \(\mathrm{\alpha }\)-d-glucosylation (E, in red) and O-acetylation (Ac, in blue) 22. Each glucosylation pattern is associated to the relevant S. flexneri type-specific (Roman numeral) and group-specific (Arabic numeral) antigenic determinants. (B) The lightly protected tetrasaccharide ABC’D’ mimicking ABCD and used in this study as a glucansucrase acceptor substrate to access S. flexneri representative oligosaccharides by a chemoenzymatic route. The chloroacetyl group at OH-2C paves the way to a hydroxyl group or an acetate (group O-factor 6) as required. The allyl aglycon and 2D-trichloroacetamide were introduced at an early stage in view of future chain elongation. All free hydroxyl groups are potential sites of enzymatic glucosylation with modifications at 3A, 3B, 4C, 4D and 6D featuring S. flexneri type/group-specific branching points. All: allyl.

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