EFFECT OF SUCROSE MONOLAURATE ON ACID PRODUCTION, LEVELS OF GLYCOLYTIC-INTERMEDIATES, AND ENZYME-ACTIVITIES OF STREPTOCOCCUS MUTANTS NCTC-10449

We studied the mechanism by which the antimicrobial compound sucrose m onolaurate inhibits Streptococcus mutans NCTC 10449 by determining its effect on the rate of acid production from glucose and sucrose and th e intracellular and extracellular levels of glycolytic intermediates. Sucrose monolaurate was more effective than either sodium laurate or s odium fluoride in inhibiting acid production at pH 7.0 from glucose. I nhibition of acid production was the same when either glucose or sucro se was the carbon source and in the presence or absence of oxygen. Qua ntitative analysis of various glycolytic intermediates revealed that t he steps inhibited by sucrose monolaurate were the reactions catalyzed by phosphofructokinase and glyceraldehyde 3-phosphate dehydrogenase a nd/or phosphoglycerate kinase. Since the activities of these enzymes i n cell-free extracts were not decreased by the addition of sucrose mon olaurate, the inhibition of acid production could not be ascribed to d irect effects on the enzymes. A decrease in the rate of acid productio n with corresponding elevations in the extracellular levels of glycoly tic intermediates indicates that sucrose monolaurate inhibits S. mutan s by altering the permeability of the cell membrane, which causes a lo ss of important metabolites.