title: Identification and molecular characterization of an N-Acetylmuraminidase, Aml, involved in Streptococcus mutans cell separation.
abstract: We previously demonstrated Streptococcus mutans produces two bacteriolytic enzymes of 100 kDa and 80 kDa (G. Yoshimura et al. Microbiol. Immunol. 48, 465-469, 2004). Here, we identified the protein sequence of these enzymes and found they come from a single gene product designated as automutanolysin (Aml). Aml has a modular design where the N-terminus contains five 13-amino-acid repeats and a C-terminal enzyme active domain. Aml selectively lyses S. mutans and S. sobrinus but no other oral streptococci. This suggests Aml possesses strong substrate specificity towards cariogenic bacteria present in the human oral cavity. Analysis of S. mutans peptidoglycan fragments released by Aml shows the enzyme is an N-acetylmuraminidase. We found Ca(2+) enhances the activity; and EGTA, EDTA and iodoacetic acid inhibit the activity. The optimum pH range for lytic activity was 6 to 7. Disruption of the aml gene in S. mutans results in the formation of a longer bacterial cell chain length that was dispersed by the addition of a low concentration of Aml. This suggests Aml is involved in S. mutans cell separation.
authors.affiliation: Department of Bacteriology, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan.
authors.forename: Goh
authors.initials: G
authors.lastname: Yoshimura
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Komatsuzawa
authors.forename: Ikue
authors.initials: I
authors.lastname: Hayashi
authors.forename: Tamaki
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Sakuo
authors.initials: S
authors.lastname: Yamada
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nakano
authors.forename: Yuko
authors.initials: Y
authors.lastname: Tomita
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kozai
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Sugai
mesh_terms: D000595:Amino Acid Sequence; D002455:Cell Division; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010641:Phenotype; D020539:Sequence Analysis, Protein; D013295:Streptococcus mutans / Q000166:cytology / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D006026:Glycoside Hydrolases; C026255:endo-N-acetylmuramidase