title: An orthologue of Bacteroides fragilis NanH is the principal sialidase in Tannerella forsythia.
abstract: Sialidase activity is a putative virulence factor of the anaerobic periodontal pathogen Tannerella forsythia, but it is uncertain which genes encode this activity. Characterization of a putative sialidase, SiaHI, by others, indicated that this protein alone may not be responsible for all of the sialidase activity. We describe a second sialidase in T. forsythia (TF0035), an orthologue of Bacteroides fragilis NanH, and its expression in Escherichia coli. Sialidase activity of the expressed NanH was confirmed by using 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid as a substrate. Biochemical characterization of the recombinant T. forsythia NanH indicated that it was active over a broad pH range, with optimum activity at pH 5.5. This enzyme has high affinity for 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid (K(m) of 32.9 +/- 10.3 microM) and rapidly releases 4-methylumbelliferone (V(max) of 170.8 +/- 11.8 nmol of 4-methylumbelliferone min(-1) mg of protein(-1)). E. coli lysates containing recombinant T. forsythia NanH cleave sialic acid from a range of substrates, with a preference for alpha2-3 glycosidic linkages. The genes adjacent to nanH encode proteins apparently involved in the metabolism of sialic acid, indicating that the NanH sialidase is likely to be involved in nutrient acquisition.
authors.affiliation: Department of Microbiology, King's College London Dental Institute, King's College London, Guy's Campus, London SE1 9RT, United Kingdom.
authors.forename: Hayley
authors.initials: H
authors.lastname: Thompson
authors.forename: Karen A
authors.initials: KA
authors.lastname: Homer
authors.forename: Susmitha
authors.initials: S
authors.lastname: Rao
authors.forename: Veronica
authors.initials: V
authors.lastname: Booth
authors.forename: Arthur H F
authors.initials: AH
authors.lastname: Hosie
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001439:Bacteroides / Q000201:enzymology*; D001441:Bacteroides fragilis / Q000201:enzymology*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006923:Hymecromone / Q000031:analogs & derivatives / Q000378:metabolism; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D009439:Neuraminidase / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D006923:Hymecromone; D009439:Neuraminidase; D019158:N-Acetylneuraminic Acid