Uptake of fructose by the sorbitol phosphotransferase of Escherichia coli K12.

Strains of Escherichia coli that are unable to grow on fructose because they lack the phosphoenolpyruvate: fructose phosphotransferases specified by ptsF and ptsX mutate to grow on media containing fructose as sole carbon source, but do not regain the function of either of the missing phosphotransferases. Instead, fructose is taken up and phosphorylated to fructose 6-phosphate by a phosphoenolpyruvate: sorbitol phosphotransferase which, in wild-type cells, is induced by sorbitol but not by fructose, but which is constitutively expressed in these mutants. The regulatory gene srlC controlling enzymes of sorbitol uptake and catabolism has been located on the E. coli genome as part of the linkage group cysI srlC attI86 pheA.