The exopolysaccharide of Klebsiella aerogens A3 (S1) (type 54). The isolation of O-acetylated octasaccharide, tetrasaccharide and trisaccharide

Abstract

The exopolysaccharide slime produced by Klebsiella aerogenes A 3 (Sl) (type 54) is an O-acetylated polysaccharide, the components of which are glucose, glucuronic acid, fucose and acetyl in the molar proportions 4:2:2:1. A phage-induced fucosidase was obtained that hydrolyses the polysaccharide to give an octasaccharide having the same constituents in the same molar proportions. This octasaccharide (O3) is considered to be the repeating unit of the polysaccharide. It is hydrolysed by other phage-induced fucosidases described earlier to release two tetrasaccharides (O1 and O2). These differ only in that tetrasaccharide O2 is acetylated. An acetylated trisaccharide of structure beta-glucosylglucuronosylfucose was prepared from tetrasaccharide O2. A further unidentified group is present. Cell-free preparations were used to acetylate the disaccharide alpha-glucuronosylfucose. From these results the structure of the octasaccharide (O3) is postulated and its significance in the biosynthesis of the polysaccharide discussed.