Fructose-1,6-Diphosphatase and Acid Hexose Phosphatase of Escherichia coli

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Abstract
The conversion of fructose-1,6-diphosphate to fructose-6-phosphate (fructose-1,6-diphosphatase activity) is essential for growth of E. coli on glycerol, acetate, or succinate, but is unnecessary for growth on hexoses or pentoses. It has sometimes been assumed that fructose-1,6-diphosphatase activity is due to a nonspecific acid hexose phosphatase. We have now obtained a number of one-step mutants which have lost the ability to grow on glycerol, succinate, or acetate, but which grow normally on hexoses; these mutants are deficient in a fructose-1,6-diphosphatase which can be assayed spectrophotometrically in the presence of Mg++ and low concentrations of substrate. These mutants still possess the non-specific acid hexose phosphatase, which does not require Mg++ and is active only at much higher concentrations of fructose-1,6-diphosphate. Evidence is presented to support the hypothesis that the newly described activity is the physiological frucotse-1,6-diphosphatase. The acid hexose phosphatase is a different enzyme whose function remains unknown.

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