earticle

영어

Streptococcus pneumoniae, the major causative agent for pneumonia, otitis media and meningitis, produces surface exoglycosidases such as neuraminidase (NanA), β-galactosidase (BgaA) and N-acetylglucosaminidase (StrH). These enzymes play critical roles for colonization and pathogenesis by sequentially hydrolyzing various glycoconjugates to penetrate host defense molecules, to expose binding sites on the surface of the epithelial cells or to obtain monosaccharides for growth. In this study, we characterized a novel β-galactosidase encoded by the bgaC gene of S. pneumoniae. The recombinant BgaC protein exhibited a highly regio- and sugar-specific hydrolysis activity for Galβ(1,3)GlcNAc moiety of oligosaccharides. Interestingly, the BgaC was shown to be expressed as a surface protein, even though it does not have a typical signal sequence or membrane anchorage motif. The bgaC mutant strains did not show detectable changes in growth or morphology compared to wild type stains when cultivated under normal laboratory conditions. However, the bgaC mutant showed higher colonization levels at 6 and 12 h post-infection in vivo than the wild type. Our data strongly indicate that S. pneumoniae BgaC is a surface-associated β-galactosidase with a specific hydrolysis activity that contributes significantly to the adherence and invasion of pneumococci in vivo and in vitro.