Inhibition of methionine gamma lyase deaminase and the growth of Porphyromonas gingivalis: A therapeutic target for halitosis/periodontitis.

BACKGROUND AND OBJECTIVES: Pathogenic infections caused by Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia can result in the production of volatile sulfur compounds (VSC's) and other toxic compounds from methionine catabolism that can lead to halitosis and periodontitis. Our aim is to block the activity of methionine gammalyase-deaminase (Mgld) of methionine catabolism to prevent halitosis/periodontitis.

DESIGNS: Cloned, expressed, Mgld protein was tested for purity by SDS-PAGE and western blotting. Mgld activity was tested by UV-vis spectroscopy and DTNB assay. Effects of Mgld inhibitor propargylglycine (PGLY) was tested on P. gingivalis growth by turbidity measurements. The effects of PGLY on oral epithelial and periodontal ligament cells in culture at different concentrations and time were tested for cell viability by MTT and Live-Dead assays. Amino acid comparisons of Mgld from different oral pathogens were done using standard bioinformatics program.

RESULTS: Propargylglycine (PGLY) inhibited purified Mgld activity completely. In vivo, PGLY is a potent inhibitor on the growth of the P. gingivalis over 24 h, grown at 25 °C and 37 °C. Correspondingly in vivo Mgld activity was also affected by PGLY. Amino acid comparisons of oral pathogens showed 100% identity on the key residues of Mgld catalysis. Mammalian oral cell lines with PGLY, showed no difference in cell death over untreated controls assessed by MTT and Live-Dead assays.

CONCLUSIONS: PGLY arrest's VSC's production by P. gingivalis. Since initial Mgld activity is inhibited subsequent enzymatic and nonenzymatic products formed will be prevented. PGLY showed no toxicity towards cultured mammalian oral cells. Thus, PGLY can serve as a mouthwash ingredient to prevent halitosis/periodontitis.