Klebsiella serotype K39: structure of an unusual capsular antigen deduced by use of a viral endoglucosidase.

Methylation analysis and graded acid hydrolysis showed that the capsular polysaccharide of Klebsiella K39 is of the "5 + 1" type and that the repeating unit contains two nonequivalent residues of D-glucopyranosyluronic acid, one of which constitutes the branch point. A decision between two possible structures, in favor of that shown below, was reached by examination of the hexasaccharide obtained by depolymerization using phage luminal diameter 39, which possessed an endo-beta-D-glucosidase. Anomeric configurations were assigned by analysis of 1H- and 13C-n.m.r. spectroscopic data for the polysaccharide and oligosaccharides derived therefrom. The following structure is proposed for the Klebsiella K39 antigen: -3(Glc beta 1-4)GlcA beta 1-2Man alpha 1-4GlcA beta 1-2Man alpha 1-3Glc beta 1- The polysaccharide is the first in the Klebsiella genus thus far reported to contain two uronic acid residues per repeating unit.