Biosynthesis of Polysaccharides in Acetobacter xylinum

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Abstract
The sequential synthesis in vitro of a heptasaccharide diphosphate prenol, containing glucose, mannose, glucuronic acid and rhamnose in the ratio 4:1:1:1 is described. The enzyme preparation consisted of EDTA‐treated Acetobacter xylinum cells and UDP‐glucose, GDO‐mannose, UDP‐glucuronic acid and TDP‐rhamnose were employed as sugar donors.The compounds soluble in chloroform/methanol/water (1:2:0.3) formed from incubations carried out under different conditions in the presence of a variety of combinations of the donors labeled with 14C, 3H or 32P were analysed by DEAE‐cellulose column chromatography, gel filtraton, partial acid hydrolysis, acetolysis, periodate oxidation, etc.The following structure is proposed for the most complex compound characterized: rhamnosyL(1 → 6)‐β‐glucosyl‐(1 → 6)‐α‐glucosyl‐(1 → 4)‐β‐glucuronyl‐(1 → 6)‐β‐mannosyl‐(1 → 3)‐β‐glucosyl‐(1 → 4)‐α‐glucosyl diphosphate prenol.The smaller oligosaccharide diphosphate prenols formed as intermediate steps are also characterized in this or in previous work [Garcia, R. C., Recondo, E. and Dankert, M. A. (1974) Eur. J. Biochem. 43, 93–105; Couso, R. O., Ielpi, L., and Damkert, M. A. (1980) Arch. Biochem. Biophys. 204, 434–443].The role of these compounds in the biosynthesis of a complex exopolysaccharide that this microorganism forms in addition to cellulose is discussed.