Summary: In contrast to a previous report, strains of were found to take up and phosphorylate the disaccharide sucrose via the phosphoenolpyruvate-dependent carbohydrate phosphotransferase system (PTS). In addition to the two soluble and general components enzymeI and HPr of the PTS, a sucrose-specific enzymeII (gene ), together with the enzymeIII, coded for by the gene , were needed for the vectorial phosphorylation of sucrose to generate intracellular sucrose 6-phosphate. This sugar phosphate is hydrolysed by a hydrolase (invertase, gene ) to generate glucose 6-phosphate and free fructose. The latter is converted to fructose 6-phosphate by an ATP-dependent fructokinase (gene ), an enzyme which is part of the sucrose and not of the fructose catabolic pathway. Analysis of different mutants of strain 1033, and of K12 derivatives carrying R' plasmids isolated from , showed that the genes , and , together with a gene for a repressor, form a genetic unit located on the chromosome of These genes and the corresponding sucrose metabolic pathway are very similar to a previously described system encoded on plasmid pUR400 and found in other enteric bacteria.


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