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Journal of Bacteriology, June 2009, p. 3623-3628, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.01618-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

An Orthologue of Bacteroides fragilis NanH Is the Principal Sialidase in Tannerella forsythia{triangledown}

Hayley Thompson,1 Karen A. Homer,1 Susmitha Rao,1 Veronica Booth,2 and Arthur H. F. Hosie1*

Department of Microbiology,1 Department of Periodontology, King's College London Dental Institute, London, United Kingdom2

Received 14 November 2008/ Accepted 17 March 2009

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 (Km of 32.9 ± 10.3 µM) and rapidly releases 4-methylumbelliferone (Vmax 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 {alpha}2-3 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.

* Corresponding author. Mailing address: Department of Microbiology, King's College London Dental Institute, Floor 28 Guy's Tower, King's College London, Guy's Campus, London SE1 9RT, United Kingdom. Phone: 44(0)20 7188 1825. Fax: 44(0)20 7188 3871. E-mail: arthur.hosie{at}kcl.ac.uk

{triangledown} Published ahead of print on 20 March 2009.

Journal of Bacteriology, June 2009, p. 3623-3628, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.01618-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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