Formation of methyl mercaptan from L-methionine by Porphyromonas gingivalis

Methyl mercaptan production by oral bacteria is thought to be one of the ma in causes of oral malodor. We examined the ability of periodontopathic Porp hyromonas gingivalis to produce methyl mercaptan from L-methionine and foun d that the invasive strains W83 and W50 produced large amounts of methyl me rcaptan, We cloned and sequenced the mgl gene encoding L-methionine-alpha - deamino-gamma -mercaptomethane-lyase (METase) from P. gingivalis W83. The s tructural mgl gene consisted of 1,200 bp and encoded a 43.3-kDa protein. To examine the role of methyl mercaptan in the pathogenesis of P. gingivalis, a METase-deficient mutant of P. gingivalis W83 was constructed. The methio nine degradation activity and virulence of the mutant (M1217) and the paren t strain (W83) in mice were compared. M1217 showed a marked decrease in the formation of methyl mercaptan from L-methionine and decreased virulence co mpared with the wild-type strain W83. These results suggest that methyl mer captan not only is one of the sources of oral malodor, but may also play a role in the pathogenicity of P. gingivalis.