title: 2-Ketoglutarate as a possible regulatory metabolite involved in cyclic AMP-dependent catabolite repression in Escherichia coli K12.
abstract: 2-Ketoglutarate--unlike any other derivative of the citric acid cycle--was found to strongly repress catabolite-sensitive genes, such as the lactose operon (lac) or the tryptophanase gene (tna), when added to cells grown in glycerol. 2-ketoglutarate affects the expression of these genes by decreasing cyclic AMP synthesis. Such inhibition of cyclic AMP synthesis requires the presence of enzyme III, a component of the phosphoenol pyruvate:sugar phosphotransferase transport system (PTS). Thus, it is proposed that 2-ketoglutarate is one of the catabolite repressors postulated by Magasanik in 1961. In addition, by studying the effect of 2-ketoglutarate in various mutants, we show the existence of a cyclic AMP-independent catabolite repression mechanism whose mediator is synthesized from 2-ketoglutarate.
mesh_terms: D000242:Cyclic AMP / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005796:Genes / Q000187:drug effects; D005798:Genes, Bacterial / Q000187:drug effects; D007656:Ketoglutaric Acids / Q000494:pharmacology*; D007700:Kinetics; D007763:Lac Operon; D012333:RNA, Messenger / Q000235:genetics; D013045:Species Specificity; D014368:Tryptophanase / Q000235:genetics; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D007656:Ketoglutaric Acids; D012333:RNA, Messenger; D000242:Cyclic AMP; D001616:beta-Galactosidase; D014368:Tryptophanase