Lysozyme Enhances the Inhibitory Effects of the Peroxidase System on Glucose Metabolism of Streptococcus mutans

The combined effect of the salivary peroxidase system and lysozyme on the glucose uptake of Streptococcus mutans NCTC 10449 was investigated. The bacteria were grown to late-exponential phase, washed, re-suspended in buffer at pH 6, and incubated with (1) 50 μg/ mL lysozyme from human milk for 60 min; (2) 7-15 μmol/L hypothiocyanous acid/hypothiocyanite for 10 min; and (3) lysozyme for 60 min prior to addition of and incubation with hypothiocyanous acid/hypothiocyanite for 10 min. Glucose uptake was initiated by adding the bacterial suspensions to 10 mL of pre-warmed 50 μmol/L glucose containing 0.98 μmol/L D-(U-14C-)-glucose, and the mixture was incubated in a shaking water-bath at 37°C. Samples were withdrawn at various time intervals, rapidly filtered through 0.45-μm membranes, washed with ice-chilled buffer, and the incorporated radioactivity determined. Lysozyme stimulated S. mutans glucose uptake slightly, but significantly inhibited S. rattus glucose metabolism. A 20-30% inhibition of radiolabeled ...