A comparative study of enzymes involved in glucose phosphorylation in oral streptococci

The properties of two enzymes involved in the phosphorylation of glucose were studied in three oral streptococci species. The glucokinase of Streptococcus mutans had a lower affinity for glucose and ATP than did those from S. salivarius and S. sanguis. The enzyme had an identical pH optimum (pH 8.0) in all three bacteria. However, the result from the phosphoenolpyruvate phosphotransferase system showed a different pattern when its activity was measured using 2-deoxyglucose with toluenized cells. Uptake studies of 2-deoxyglucose also revealed that the three microorganisms had different affinities for this compound. This glucose analogue strongly inhibited the acid production of S. salivarius, but did not affect the glycolysis of the other two bacteria.