XYLOSE TRANSPORT INSENSITIVITY TO CATABOLITE INHIBITION BY PHOSPHOENOLPYRUVATE - SUGAR PHOSPHOTRANSFERASE SYSTEM IN TETRAGENOCOCCUS-HALOPHILA

Tetragenococcus halophila accumulates glucose and 2-deoxyglucose (dGlc ) via the phosphoenolpyruvate:sugar phosphotransferase system (PTS), a nd pentoses, maltose, and glycerol via non-PTS carriers. Based on the discovery that xylose metabolism in T. halophila was subject to catabo lite repression but not to catabolite inhibition, we designed a select ion protocol for thermosensitive mutants pleiotropically unable to use sugars. One such mutant was a ptsI mutant with a thermosensitive enzy me I (EI) of the PTS (leaky at 30 degrees C). Using this ptsI mutant, catabolite inhibition was studied. dGlc was more strongly inhibitory o f glycerol uptake in the mutant than in the parent because of the leak y ptsI mutation. Thermoinactivation of EI at 42 degrees C resulted in the total loss of uptake of PTS sugars and in the virtual abolishment of glycerol uptake. However, xylose uptake of the ptsI mutant was scar cely inhibited by dGlc even after thermoinactivation of EI, These resu lts suggest that sensitivities of non-PTS uptakes to PTS-mediated inhi bition vary among non-PTS sugars.