Isolation and characterisation of sialidase from a strain of Streptococcus oralis

J Med Microbiol. 2000 Mar;49(3):235-244. doi: 10.1099/0022-1317-49-3-235.

Abstract

Streptococcus oralis, the most virulent of the viridans streptococci, produces a sialidase and this exo-glycosidase has been implicated in the disease process of a number of pathogens. The sialidase of S. oralis strain AR3 was purified in order to understand the characteristics of this putative virulence determinant. The enzyme isolated as a high mol. wt aggregate (c. 325 kDa) was purified 4520-fold from late exponential phase cultures by a combination of ultrafiltration, ammonium sulphate precipitation, ion-exchange and gel filtration chromatography. The sialidase component had a mol.wt of 144 kDa as determined by SDS-PAGE analysis. The purified sialidase released N-acetylneuraminic acid from a range of sialoglycoconjugates including human alpha1-acid glycoprotein, bovine submaxillary mucin, colominic acid and sialyl-alpha2,3- and sialyl-alpha2,6-lactose. Also, N-glycolylneuraminic acid was cleaved from bovine submaxillary mucin. The sialidase had a Km of 11.8 microM for alpha1-acid glycoprotein, was active over a broad pH range with a pH optimum of 6.0 and cleaved alpha2,3-, alpha2,6- and alpha2-8-sialyl glycosidic linkages with a marked preference for alpha2,3-linkages. The enzyme was competitively inhibited by the sialic acid derivative, 2,3-dehydro-N-acetylneuraminic acid, with a K(IC) of 1.2 microM. The characteristics of the purified sialidase would support a nutritional role for this enzyme that may be significant in the proliferation of this organism in the oral cavity and at extra-oral sites in association with life-threatening infections.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Gel
  • Chromatography, Ion Exchange
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Kinetics
  • Molecular Weight
  • Neuraminidase / antagonists & inhibitors
  • Neuraminidase / chemistry
  • Neuraminidase / isolation & purification*
  • Neuraminidase / metabolism
  • Sialoglycoproteins / metabolism
  • Streptococcus oralis / enzymology*
  • Streptococcus oralis / pathogenicity
  • Substrate Specificity
  • Ultrafiltration
  • Virulence

Substances

  • Sialoglycoproteins
  • Neuraminidase