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

Abstract

The combined effect ofthe 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 pg/ mL lysozyme from human milk for 60 min; (2) 7-15 gmol/L hypothiocyanous acid/hypothiocyanite for 10 min; and (3) lysozyme for 60 min prior to addition ofand incubation with hypothiocyanous acid/hypothiocyanite for 10 min. Glucose uptake was initiated by adding the bacterial suspensions to 10 mL ofpre-warmed 50 pmol/L glucose containing 0.98 pimol/L D-(U-"4C-)-glucose, and the mixture was incubated in a shaking water-bath at 370C. Samples were withdrawn at various time intervals, rapidly filtered through 0.45-pm membranes, washed with ice-chilled buffer, and the incorporated radioactivity determined.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 ofradiolabeled glucose incorporation was observed with hypothiocyanous acid/hypothiocyanite alone. Incubationofthe bacteriawithlysozyme priortoaddition ofhypothiocyanous acid/hypothiocyanite containingperoxidase resulted in a total inhibition ofthe glucose uptake. In contrast, lysozyme in combination with hypothiocyanous acid/hypothiocyanite without peroxidase gave only a 30-50% inhibition. The addition of 5 mmol/L dithiothreitol after incubation withlysozyme and hypothiocyanous acid/hypothiocyanite eliminated the inhibition of the bacterial glucose uptake. The viability ofS. mutans was not affected by treatment with any ofthe components used. Our results indicate that physiological concentrations of lysozyme and the salivary peroxidase system components have a synergistic effect which results in a significant inhibition of glucose metabolism by S. mutans. J Dent Res 71 (3): 484-490, March, 1992

Lysozyme and Lactoperoxidase Inhibit the Adherence of Streptococcus mutans NCTC 10449 (Serotype c) to Saliva-Treated Hydroxyapatite in vitro

“…This is in accordance with previous studies of the same S.mutans strain and human LZ Tenovuo, 1991: Wang andGermaine, 1991;Lenander-Lumikari et al, 1992], in dicating no bactericidal effect of LZ against this strain. Thus, it is most likely that the observed inhibition of the adherence of S.mutans to saliva-coated apatite was due to LZ, but not because o f any cell lysis induced by this en zyme.…”

The sensitivity of Porphyromonas gingivalis and Fusobacterium nucleatum to different (pseudo)halide-peroxidase combinations compared with mutans streptococci

“…Physiological concentrations of (pseudo)halides and peroxidases were used. Previous studies on A. actinomycetemcomitans and S. mutans have shown that these halide concentrations, in combination with LP/MP and H 2 O 2 , cause signi®cant antibacterial effect [10,14], and that the peroxidase activities rapidly produce OSCN À from SCN À in the presence of H 2 O 2 [33]. H 2 O 2 concentration is not measurable in saliva, because it is actively produced and depleted in biochemical reactions.…”

Does Variability in Salivary Protein Concentrations Influence Oral Microbial Ecology and Oral Health?

“…Many salivary proteins interact in vitro in ways that affect their joint interaction with oral bacteria. Lactoferrin, slgA, and lysozyme all may increase inhibitory effects of peroxidase (Tenovuo et al, 1982;Lenander-Lumikari et al, 1992a), and slgA against bacterial iron-binding proteins may enhance bacteriostatic iron-sequestration by lactoferrin (Ellison et al, 1988). On the other hand, bactericidal actions of lactoferrin can be blocked or enhanced by slgA specific to particular species (Lassiter et al, 1987;Motley and Arnold, 1987).…”