Production of specific glycosidase activities by Streptococcus intermedius strain UNS35 grown in the presence of mucin

1 Oral Microbiology, Royal College of Surgeons Department of Dental Sciences, Faculty of Clinical Dentistry, King's College School of Medicine and Dentistry, Caldecot Road, Denmark Hill, London SE5 9RW * Department of Oral Microbiology, London Hospital Medical College, Turner Street, Whitechapel, London E1 2AD Received March 3, 1994 Accepted March 8, 1994 An isolate of Streptococcus intermedius from a brain abscess showed neuraminidase (sialidase), β-D-galactosidase, N-acetyl-β-D-glucosaminidase and N-acetyl-β-D-galactosaminidase activities. The optimal pH values of these enzymes were 5.5-6.0, 5.5-6.0, 5.0-5.5 and 5.0-5.5, respectively. The k m of the enzymes varied according to whether the type of substrate was chromogenic or fluorogenic; sialidase was most active at the lowest substrate concentrations, with a k m of 0.01 mM. In semi-defined medium, with porcine gastric mucin—a model glycoprotein—as the sole source of fermentable carbohydrate, levels of the glycosidases were significantly increased. Addition of glucose to the mucin-containing medium, or growth of cells in media supplemented with glucose alone, repressed glycosidic activities and the majority of these were cell-associated. S. intermedius cells from cultures grown with mucin were able, simultaneously, to transport via sugar: phosphoenolpyruvate phosphotransferase (PTS) systems, monosaccharides which are constituents of carbohydrate side chains of glycoproteins. These cells also possessed significant levels of neuraminate-pyruvate lyase, involved in the intracellular catabolism of neuraminic acid; this was absent from cells grown with glucose. These mechanisms, collectively, may facilitate the persistence and growth of S. intermedius in vivo .