Neuraminidase associated with coliphage E that specifically depolymerizes the Escherichia coli K1 capsular polysaccharide.
Plaque morphology indicated that the five Escherichia coli K1-specific bacteriophages (A to E) described by Gross et al. (R. J. Gross, T. Cheasty, and B. Rowe, J. Clin. Microbiol. 6:548-550, 1977) encode K1 depolymerase activity that is present in both the bound and free forms. The free form of the enzyme from bacteriophage E was purified 238-fold to apparent homogeneity and in a high yield from ammonium sulfate precipitates of cell lysates by a combination of CsCl density gradient ultracentrifugation, gel filtration, and anion-exchange chromatography. The enzyme complex had an apparent molecular weight of 208,000, as judged from its behavior on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and was dissociated by sodium dodecyl sulfate at 100 degrees C to yield two polypeptides with apparent molecular weights of 74,000 and 38,500. Optimum hydrolytic activity was observed at pH 5.5, and activity was strongly inhibited by Ca2+; the Km was 7.41 X 10(-3) M. Rapid hydrolysis of both the O-acetylated and non-O-acetylated forms of the K1 antigen, an alpha 2----8-linked homopolymer of N-acetylneuraminic acid, and of the meningococcus B antigen was observed. Limited hydrolysis of the E. coli K92 antigen, an N-acetylneuraminic acid homopolymer containing alternating alpha 2----8 and alpha 2----9 linkages, occurred, but the enzyme failed to release alpha 2----3-, alpha 2----6-, or alpha 2----9-linked sialic residues from a variety of other substrates.
D000942:Antigens, Bacterial; D016667:Bacterial Capsules; D003090:Coliphages / Q000201:enzymology*; D004926:Escherichia coli; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D009439:Neuraminidase / Q000302:isolation & purification / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D013379:Substrate Specificity
D000942:Antigens, Bacterial; D011135:Polysaccharides, Bacterial; C036962:capsular polysaccharide K1; D009439:Neuraminidase