The isocitrate dehydrogenase phosphorylation cycle: regulation and enzymology.
Isocitrate dehydrogenase (IDH) of Escherichia coli is regulated by phosphorylation and dephosphorylation. This phosphorylation cycle controls the flow of isocitrate through the glyoxylate bypass, a pathway which bypasses the CO2 evolving steps of the Krebs' cycle. IDH is phosphorylated at a single serine which resides in its active site. Phosphorylation blocks isocitrate binding, thereby inactivating IDH. The IDH phosphorylation cycle is catalyzed by a bifunctional protein kinase/phosphatase. The kinase and phosphatase reactions appear to be catalyzed at the same site and may share some catalytic steps. A variety of approaches have been used to examine the IDH phosphorylation cycle in the intact organism. The picture which has emerged is one of an exquisitely sensitive and flexible system which is capable of adapting efficiently to the environment both inside and outside the cell.
LaPorte
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Department of Biochemistry, University of Minnesota, Minneapolis 55455.
D001426:Bacterial Proteins / Q000378:metabolism*; D002952:Citric Acid Cycle; D004734:Energy Metabolism; D004926:Escherichia coli / Q000201:enzymology*; D006038:Glyoxylates / Q000378:metabolism; D007521:Isocitrate Dehydrogenase / Q000378:metabolism*; D007523:Isocitrates / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases
D001426:Bacterial Proteins; D006038:Glyoxylates; D007523:Isocitrates; C034219:isocitric acid; D007521:Isocitrate Dehydrogenase; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; C042301:isocitrate dehydrogenase kinase; C042300:isocitrate dehydrogenase phosphatase; D010749:Phosphoprotein Phosphatases