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ABSTRACT: The object of this work was to study the effect of mutations damaging protein components of the phosphoenolpyruvate-dependent phosphotransferase system (PTS) of E. coli on the regulation of the activity of catabolite-sensitive operons. Mutations ptsI and ptsH affecting the activity of the enzyme I and HPr protein made the synthesis of catabolite-sensitive enzymes resistant to the action of glucose, and at the same time decreased the rate of transport of this compound. Mutation tgl affecting the activity of the glucose enzyme II lead to the same effect on the enzyme syntheses, though utilization was not altered in this case. The disturbance of beta-galactosidase synthesis in ptsI and ptsH mutants is due to interference of pts mutations into transcription of the lac operon at the lac promoter level. It is concluded that the proteins of the Escherichia coli PTS take part not only in glucose transport, but are also involved in the regulation of transcription of the catabolite sensitive operons.