Two additional bacteriophage-associated glycan hydrolases cleaving ketosidic bonds of 3-deoxy-D-manno-octulosonic acid in capsular polysaccharides of Escherichia coli.

Two bacteriophages degrading 3-deoxy-D-manno-2-octulosonic acid-(KDO)-containing capsules of Escherichia coli strains were identified. Using modifications of the thiobarbituric acid assay, it was shown that each phage contains a glycan hydrolase activity cleaving one type of ketosidic linkage of KDO. Thus, the enzyme from phage phi 95 catalyzes the hydrolysis of beta-octulofuranosidonic linkages of the K95 glycan; and phi 1092, the alpha-octulopyranosidonic linkages of the K? antigen of E. coli LP1092. No cross-reactivity of the phage enzymes with other KDO-containing capsular polysaccharides was observed.