Release of glucose-mediated catabolite repression due to a defect in the membrane fraction of phosphoenolpyruvate: mannose phosphotransferase system in Pediococcus halophilus

Abstract

A spontaneous mutant 9R-4 resistant to 2-deoxyglucose (2DG) was derived from a wild-type strain Pediococcus halophilus I-13. Phosphoenolpyruvate (PEP)-dependent glucose-6-phosphate formation by the permeabilized 9R-4 cells was less than 5% of that observed with the parent I-13. In vitro complementation of PEP-dependent 2DG-6-phosphate formation was assayed with combination of the cytoplasmic and membrane fractions prepared from the I-13 and the mutants (9R-4, and X-160 isolated from nature), which were defective in PEP:mannose phosphotransferase system (man:PTS). The defects in man:PTS of both the strain 9R-4 and X-160 were restricted to the membrane fraction (e.g. EIIman), not to the cytoplasmic one. Kinetic studies on the glucose transport with intact cells and iodoacetate-treated cells also supported the presence of two distinct transport systems in this bacterium as follows: (i) The wild-type I-13 possessed a high-affinity man:PTS (Km = 11 microM) and a low-affinity proton motive force driven glucose permease (GP) (Km = 170 microM). (ii) Both 9R-4 and X-160 had only the low-affinity system (Km = 181 microM for 9R-4, 278 microM for X-160). In conclusion, a 2DG-induced selective defect in the membrane component (EIIman) of the man:PTS could partially release glucose-mediated catabolite repression but not fructose-mediated catabolite repression in soy pediococci.