title: Metabolism of glycoprotein-derived sialic acid and N-acetylglucosamine by Streptococcus oralis.
abstract: Nine strains of Streptococcus oralis, isolated from blood cultures of patients with infective endocarditis or from the oral cavity as part of the normal flora, were examined for their ability to elaborate sialidase (neuraminidase) and N-acetylglucosaminidase, enzymes which are involved in the degradation of glycoproteins. Both glycosidases were induced when bacteria were grown in a minimal medium supplemented with porcine gastric mucin, a model glycoprotein, and repressed when growth occurred in the presence of glucose. Cell-free extracts mucin-grown cultures expressed elevated levels of N-acetylneuraminate pyruvate-lyase (the first intracellular enzyme in the pathway of N-acetylneuraminate catabolism), N-acetylglucosamine (glcNAc)-6-phosphate deacetylase and glucosamine-6-phosphate deaminase (enzymes involved in the intracellular catabolism of GlcNAc 6-phosphate); activity of each of these intracellular enzymes was markedly repressed when bacteria were grown in media supplemented with alpha 1-acid glycoprotein, a major component of human plasma. Cells from these cultures expressed high levels of sialidase, N-acetylglucosaminidase, and the intracellular enzymes involved in the catabolism of N-acetyl-sugars released by action of these glycosidases. High-resolution 1H-NMR spectroscopy of spent culture supernatants revealed that sialic acid and GlcNAc residues of the molecularly mobile oligosaccharide side-chains of alpha 1-acid glycoprotein had been hydrolysed and the released sugars internalized by the bacteria. These data indicate that S. oralis has the ability to hydrolyse constituents of oligosaccharide side-chains of host-derived glycoproteins and to utilize simultaneously these released carbohydrates. The biochemical characteristics induced by the growth of S. oralis on glycoproteins may play a role in the survival and persistence of these bacteria at the infection site in vivo.
authors.affiliation: Joint Microbiology Research Unit, King's College School of Medicine and Dentistry, Faculty of Clinical Dentistry, Caldecot Road, London SE5 9RW, UK.
authors.forename: K A
authors.initials: KA
authors.lastname: Homer
authors.affiliation: Joint Microbiology Research Unit, King's College School of Medicine and Dentistry, Faculty of Clinical Dentistry, Caldecot Road, London SE5 9RW, UK.
authors.forename: S
authors.initials: S
authors.lastname: Kelley
authors.affiliation: Department of Chemistry, King's College (Strand Campus), University of London, The Strand, London WC2R 2LS, UK.
authors.forename: J
authors.initials: J
authors.lastname: Hawkes
authors.affiliation: Joint Microbiology Research Unit, King's College School of Medicine and Dentistry, Faculty of Clinical Dentistry, Caldecot Road, London SE5 9RW, UK.
authors.forename: D
authors.initials: D
authors.lastname: Beighton
authors.affiliation: Inflammation Research Group, The London Hospital Medical College, Ashfield Street, London E1 2AD, UK.
authors.forename: M C
authors.initials: MC
authors.lastname: Grootveld
mesh_terms: D000117:Acetylglucosamine / Q000378:metabolism*; D000118:Acetylglucosaminidase / Q000378:metabolism; D019747:Aldose-Ketose Isomerases; D000581:Amidohydrolases / Q000378:metabolism; D016470:Bacteremia / Q000382:microbiology; D001426:Bacterial Proteins / Q000378:metabolism*; D002238:Carbohydrate Epimerases / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry*; D006801:Humans; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D009055:Mouth / Q000382:microbiology; D019158:N-Acetylneuraminic Acid; D009439:Neuraminidase / Q000378:metabolism; D009961:Orosomucoid / Q000378:metabolism; D007652:Oxo-Acid-Lyases / Q000378:metabolism; D012794:Sialic Acids / Q000378:metabolism*; D013290:Streptococcal Infections / Q000382:microbiology; D013291:Streptococcus / Q000201:enzymology / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D006023:Glycoproteins; D009961:Orosomucoid; D012794:Sialic Acids; D009439:Neuraminidase; D000118:Acetylglucosaminidase; D000581:Amidohydrolases; C018717:N-acetylglucosamine-6-phosphate deacetylase; C020582:glucosamine-6-phosphate isomerase; D007652:Oxo-Acid-Lyases; C018728:N-acetylneuraminate lyase; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; D019158:N-Acetylneuraminic Acid; D000117:Acetylglucosamine