The role of phosphotransferase-mediated syntheses of fructose 1-phosphate and fructose 6-phosphate in the growth of Escherichia coli on fructose.

Abstract

Mutants of Escherichia coli impaired in fructose 1-phosphate kinase activity (Fpk) accumulate fructose 1-phosphate from fructose, which arrests their growth. Phenotypic revertants to fructose tolerance have lost either the histidine-containing protein (HPr) or enzyme I of the phosphoenolpyruvate phosphotransferase system ( ctr ), and consequently utilize neither fructose nor glucose, or an enzyme II specific for the uptake of fructose and its concomitant phosphorylation to fructose 1-phosphate (PtsF). However, PtsF — -mutants can still grow on high concentrations ( > 2 mM) of fructose, and take up this sugar via a low-affinity enzyme II designated PtsX that effects its uptake and phosphorylation to fructose 6-phosphate. Mutants of the Hfr-strain KL16 were isolated that lacked PtsF, or PtsF and PtsX, activities. The consequence to, and rôle of these functions in, the uptake and metabolism of fructose are described.