Glucose transport in Streptococcus salivarius. Evidence for the presence of a distinct phosphoenolpyruvate: glucose phosphotransferase system which catalyses the phosphorylation of alpha-methyl glucoside.
A spontaneous mutant of Streptococcus salivarius ATCC 25975 was isolated by inoculating an agar medium containing 11 mM lactose and 0.5 mM 2-deoxyglucose. This mutant grew poorly on 5 mM glucose but almost as well as the parental strain on 110 mM glucose. Uptake of 2-deoxyglucose was abolished by the mutation, and phosphoenolpyruvate: glucose phosphotransferase activity could not be detected with toluenized cells under normal conditions when the glucose concentration was below 5 mM. Data from growth experiments, glycolysis, and uptake studies indicated the presence of a second phosphoenolpyruvate: glucose phosphotransferase system that could catalyze the phosphorylation of alpha-methyl glucoside. The activity of this system was detected by a spectrophotometric assay coupled with lactate dehydrogenase and by a radioactive isotope method using methyl alpha-D-[U-14C] glucoside. The phosphorylation was phosphoenolpyruvate dependent. The apparent Km of the system for glucose and alpha-methyl glucoside was approximately 20 mM. Studies with energy poisons ruled out the possibility of an active transport system, and accumulation of alpha-methyl glucoside argued against facilitated diffusion. It was concluded that the other glucose transport system which allowed growth of the mutant strain of S. salivarius was a second phosphoenolpyruvate: glucose phosphotransferase system.
D001692:Biological Transport; D004058:Diffusion; D005947:Glucose / Q000494:pharmacology; D006019:Glycolysis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism*; D008759:Methylglycosides / Q000378:metabolism*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010766:Phosphorylation; D013291:Streptococcus / Q000378:metabolism*
D008757:Methylglucosides; D008759:Methylglycosides; C027020:methylglucoside; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; D005947:Glucose