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3-Chloro-DL-alanine resistance by L-methionine-alpha-deamino-gamma-mercaptomethane-lyase activity
Mamiko Yoshimura1, Yoshio Nakano, Haruka Fukamachi
1Department of Preventive Dentistry, Kyushu University Faculty of Dental Science, 3-1-1 Maidashi, Higashi-ku, 812-8582, Fukuoka, Japan.
Abstract:
The antibacterial agent 3-chloro-DL-alanine (3CA) is an inhibitor of peptidoglycan synthesis. Fusobacterium nucleatum and Porphyromonas gingivalis, the bacteria responsible for oral malodor, are shown to be resistant to 1 mM 3CA, whereas Streptococcus mutans and Escherichia coli are sensitive to this antibacterial agent at the same concentration. We isolated the 3CA resistance gene from F. nucleatum and showed that the gene encodes an L-methionine-alpha-deamino-gamma-mercaptomethane-lyase that catalyzes the alpha,gamma-elimination of L-methionine to produce methyl mercaptan. The enzyme also exhibits 3CA chloride-lyase (deaminating) activity. This antibacterial agent is expected to be useful for specific selection of malodorous oral bacteria producing high amounts of methyl mercaptan.
Insights
3-chloro-DL-alanine (3CA) resistance in oral bacteria like Fusobacterium nucleatum was investigated. A gene conferring resistance was identified, encoding an enzyme that produces methyl mercaptan, a key compound in oral malodor.
Area of Science:
- Microbiology
- Biochemistry
- Oral Health
Background:
- Oral malodor is often caused by specific bacteria.
- Peptidoglycan synthesis is a target for antibacterial agents.
Purpose of the Study:
- To investigate the resistance of oral bacteria to 3-chloro-DL-alanine (3CA).
- To identify the genetic basis of 3CA resistance in Fusobacterium nucleatum.
- To characterize the enzyme responsible for 3CA resistance and its role in methyl mercaptan production.
Main Methods:
- Bacterial susceptibility testing with 3CA.
- Gene isolation and cloning from Fusobacterium nucleatum.
- Enzyme activity assays, including L-methionine degradation and 3CA chloride-lyase activity.
Main Results:
- Fusobacterium nucleatum and Porphyromonas gingivalis showed resistance to 1 mM 3CA, unlike Streptococcus mutans and Escherichia coli.
- A 3CA resistance gene was isolated from F. nucleatum.
- The gene encodes L-methionine-alpha-deamino-gamma-mercaptomethane-lyase, which produces methyl mercaptan from L-methionine and exhibits 3CA chloride-lyase activity.
Conclusions:
- The identified enzyme is responsible for 3CA resistance in F. nucleatum.
- This enzyme's ability to produce methyl mercaptan suggests a link between 3CA resistance and oral malodor.
- 3CA may be a selective agent for targeting malodorous oral bacteria.
