title: Inactivation of cell-associated fructosyltransferase in Streptococcus salivarius.
abstract: In stationary phase, 95% of the fructosyltransferase (FTase) activity of Streptococcus salivarius ATCC 25975 was found associated with the cells. Within the first 15 min after inoculation into fresh medium, the specific activity of cell-associated FTase decreased by 92% of its initial value. After this period of initial loss, the enzyme was synthesized during exponential growth until a maximum level equivalent to that present before inoculation was obtained. The inactivation of FTase was also demonstrated in a nongrowing system. Washed cell suspensions incubated at 37 degrees C in 200 mM potassium phosphate buffer (pH 6.5) containing 10 microM Cu2+ lost 80 to 95% of their FRase activity after 30 min. This loss could be prevented by the addition of histidine, cysteine, or Ca2+ to the suspension mixture. A factor(s) essential for the inactivation of cell-associated FTase could itself be preferentially inactivated by heating cells at 40 degrees C for periods of up to 3 h, or by storage of cells at 0 to 4 degrees C for several days in a low-ionic-strength, low-pH, potassium phosphate buffer. Treatment of cells with the N-acetylmuramidase enzyme M-1, in the presence of 0.5 M melezitose, resulted in the release of FTase from the cell. The released enzyme was recovered in the supernatant fraction after centrifugation at 160,000 x g for 90 min. Comparison of solubilized active and inactivated FTase preparations by polyacrylamide gel electrophoresis demonstrated that the inactivation of cell-associated FTase activity was associated with the loss of specific protein bands.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D003470:Culture Media; D003545:Cysteine / Q000494:pharmacology; D005632:Fructose / Q000037:antagonists & inhibitors / Q000378:metabolism; D006602:Hexosyltransferases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D013291:Streptococcus / Q000201:enzymology* / Q000254:growth & development; D013395:Sucrose / Q000037:antagonists & inhibitors / Q000378:metabolism; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D005632:Fructose; D013395:Sucrose; D006602:Hexosyltransferases; C021451:inulosucrase; D003545:Cysteine; D002118:Calcium