|MadSci Network: Molecular Biology|
Dear Robert, Hopefully this prokaryotic explanation will answer your question. When glucose is present in the growth media, it will be transported into the cell by the phosphotransferase system (PTS) and phosphorylated to glucose-6-phosphate. The enzyme IIAglc is one of the proteins involved in the PTS and plays a major role in the PST cAMP regulation. IIAglc modulates the adenylate cyclase activity; this modulation is dependent on the phosphorylation state of IIAglc. In its phosphorylated form, IIAglc will activate adenylate cyclase, whereas, in the unphosphorylated form, IIAglc will inhibit adenylate cyclase activity and thereby regulate the cAMP levels. High glucose levels decrease the IIAglc phosphorylation, thus promoting the unphosphorylated form. This yields a decrease in adenylate cyclase activity and subsequently downregulation of cAMP production. On the other hand, when glucose levels are low, the phosphorylated form of IIAglc is enhanced, thus causing an activation of adenylate cyclase and an increase in cAMP levels. Best regards, Mette Skinbjerg References Peterkofsky A. Redistribution of phosphate pools and the regulation of Escherichia coli adenylate cyclase activity. Arch Biochem Biophys. 1988 Sep;265(2):227-33. Review. Notley-McRobb, Death A, Ferenci T. The relationship between external glucose concentration and cAMP levels inside Escherichia coli: implications for models of phosphotransferase- mediated regulation of adenylate cyclase. Microbiology. 1997 Jun;143 ( Pt 6):1909-18. ReddyP, Kamireddi M. Modulation of Escherichia coli adenylyl cyclase activity by catalytic- site mutants of protein IIA(Glc) of the phosphoenolpyruvate:sugar phosphotransferase system. J Bacteriol. 1998 Feb;180(3):732-6. Krin E, Sismeiro O, Danchin A, Bertin PN. The regulation of Enzyme IIA(Glc) expression controls adenylate cyclase activity in Escherichia coli. Microbiology. 2002 May;148(Pt 5):1553-9. Kao KC, Tran LM, Liao JC. A global regulatory role of gluconeogenic genes in Escherichia coli revealed by transcriptome network analysis. J Biol Chem. 2005 Oct 28;280(43):36079-87. Epub 2005 Aug 31.
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