Enzyme Characterization of l-Methionine γ-Lyase from Porphyromonas gingivalis

Signature Grand, Davie, Florida, USA

Objective. In this study, we characterized the enzyme l -methionine γ-lyase from Porphyromonas gingivalis, a contributor to periodontal disease. Background. Oral malodor (halitosis) is caused mainly by volatile sulfur compounds (VSCs), such as hydrogen sulfide, methyl mercaptan, and dimethyl sulfide. It is thought that these highly toxic compounds are involved in the induction or progression of periodontal disease. It has been proposed that methyl mercaptan not only may be responsible for oral malodor but also may contribute to the pathogenesis of periodontal disease. l-Methionine γ-lyase (EC 4.4.4.11) catalyzes the α,γ elimination of methionine to produce methanethiol (methyl mercaptan), α-ketobutyrate and ammonia. This enzyme has been detected in several anaerobic nonoral microorganisms and has been implicated as a major pathogen in adult periodontitis. However, little is known about the role of the enzyme l -methionine γ-lyase and its product methyl mercaptan in the pathogenesis of oral microorganisms. Results. The enzyme had its highest rate of methyl mercaptan production during the first 15 min of the reaction, had an optimum activity at ~ pH 7.0 and had its highest activity at an apparent temperature of 55°C. Rate of methyl mercaptan production was greatest when the substrate concentration was between 10-100 mM. However, concentrations above 100 mM seem to inhibit lmethionine lyase activity. Conclusion. If l -methionine γ-lyase activity is responsible for the pathogenesis of this organism, future studies could lead to the inactivation of this enzyme and control the progression of periodontal disease.