title: On the specificity of a bacteriophage-borne endoglycanase for the native capsular polysaccharide produced by Klebsiella pneumoniae SK1 and its derived polymers.
abstract: The specificity of the endoglycanase associated with the bacteriophage phi SK1 particles was tested on the native capsular polysaccharide produced by Klebsiella pneumoniae serotype SK1 and on three chemically modified polymers derived from it. The primary structure of the SK1 capsular polysaccharide is: [formula: see text] and the beta 1-3 linkage between the glucose and the galactose residues is the one cleaved by the phage enzyme. The enzyme activity was assayed on the deacetylated polysaccharide and on two derivatives obtained by removal of both the side-chain sugars and of only the alpha-D-galactosyl unit, respectively. The endoglycanase was more active on the deacetylated polysaccharide than on the native one, suggesting that the presence of the acetyl groups interferes with the enzyme-polysaccharide interaction. A possible role of the acetyl groups in the control of the polysaccharide chain length and hence on the rheological behaviour of the capsule cannot be ruled out, as already indicated for other bacterial polysaccharides. On the contrary, the removal of the side chains, either complete or selective, caused the modification of the recognition site in such a way that the enzymatic depolymerization no longer occurred. Therefore, it can be inferred that the phi SK1 endoglycanase requires the presence of both the side chain sugars to exhibit its cleaving activity, although this latter is in the main chain.
authors.affiliation: Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Università degli Studi di Trieste, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Cescutti
authors.forename: S
authors.initials: S
authors.lastname: Paoletti
mesh_terms: D001435:Bacteriophages / Q000201:enzymology*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006026:Glycoside Hydrolases / Q000378:metabolism*; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D011135:Polysaccharides, Bacterial; D006026:Glycoside Hydrolases