Identification and Molecular Characterization of an <i>N</i>‐Acetylmuraminidase, Aml, Involved in <i>Streptococcus mutans</i> Cell Separation
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- Goh Yoshimura
- Department of Bacteriology Hiroshima University Graduate School of Biomedical Sciences Hiroshima Hiroshima 734‐8553 Japan
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- Hitoshi Komatsuzawa
- Department of Bacteriology Hiroshima University Graduate School of Biomedical Sciences Hiroshima Hiroshima 734‐8553 Japan
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- Ikue Hayashi
- Research Facility Hiroshima University Faculty of Dentistry Hiroshima Hiroshima 734‐8553 Japan
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- Tamaki Fujiwara
- Department of Bacteriology Hiroshima University Graduate School of Biomedical Sciences Hiroshima Hiroshima 734‐8553 Japan
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- Sakuo Yamada
- Department of Microbiology Kawasaki Medical School Kurashiki Okayama 701‐0192 Japan
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- Yoshio Nakano
- Department of Preventive Dentistry Kyushu University Faculty of Dental Science Fukuoka Fukuoka 812‐8582 Japan
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- Yuko Tomita
- Department of Bacteriology Hiroshima University Graduate School of Biomedical Sciences Hiroshima Hiroshima 734‐8553 Japan
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- Katsuyuki Kozai
- Department of Pediatric Dentistry Hiroshima University Graduate School of Biomedical Sciences Hiroshima Hiroshima 734‐8553 Japan
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- Motoyuki Sugai
- Department of Bacteriology Hiroshima University Graduate School of Biomedical Sciences Hiroshima Hiroshima 734‐8553 Japan
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<jats:title>Abstract</jats:title><jats:p>We previously demonstrated <jats:italic>Streptococcus mutans</jats:italic> 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 <jats:italic>S. mutans</jats:italic> and <jats:italic>S. sobrinus</jats:italic> but no other oral streptococci. This suggests Aml possesses strong substrate specificity towards cariogenic bacteria present in the human oral cavity. Analysis of <jats:italic>S. mutans</jats:italic> peptidoglycan fragments released by Aml shows the enzyme is an <jats:italic>N</jats:italic>‐acetylmuraminidase. We found Ca<jats:sup>2+</jats:sup> 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 <jats:italic>aml</jats:italic> gene in <jats:italic>S. mutans</jats:italic> 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 <jats:italic>S. mutans</jats:italic> cell separation.</jats:p>
収録刊行物
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- Microbiology and Immunology
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Microbiology and Immunology 50 (9), 729-742, 2006-09
Wiley
