Dehydrogenase activity involved in the uptake of glucose 6-phosphate by a bacterial membrane system.

Membranes prepared from Escherichia coli induced or constitutive for glucose 6-phosphate transport accumulate this compound from the medium. The transport is independent of the phosphotransferase system, insofar as a mutant deficient in Enzyme I of this system yields membranes fully active in glucose 6-phosphate uptake; and the addition of phosphoenolpyruvate to induced wild type membranes did not stimulate glucose 6-phosphate uptake. Both the rate and extent of uptake are, however, stimulated several-fold in the presence of either D( -)-lactate or succinate. In the case of the D( -)-lactic dehydrogenase activity there is far more pyruvate produced than glucose 6-phosphate transported. Evidence presented indicates that it is the free glucose 6-phosphate which is accumulated, and that this material is freely exchangeable with external compound.