Regulatory interactions involving the proteins of the phosphotransferase system in enteric bacteria

Abstract

Sugar uptake and cytoplasmic inducer generation as well as cyclic AMP synthesis are regulated by the phosphoenolpyruvate:sugar phosphotransferase system (PTS) in Gram‐negative enteric bacteria. In these organisms, the free form of the glucose‐specific Enzyme IIA (IIA^glc) of the PTS, which can be phosphorylated on a histidyl residue by PEP and the PTS energy coupling proteins, inhibits the activities of non‐PTS carbohydrate permeases and catabolic enzymes. By contrast, the phosphorylated form of IIA^glc appears to activate adenylate cyclase, the cyclic AMP biosynthetic enzyme. What is known of the molecular details of these regulatory interactions will be summarized, and a novel regulatory mechanism involving the fructose repressor, FruR, which controls the transcription of genes encoding enzymes which catalyze reactions in central pathways of carbon metabolism, will be presented.