alpha-Ketoglutarate dehydrogenase complex of Escherichia coli. A hybrid complex containing pyruvate dehydrogenase subunits from pyruvate dehydrogenase complex.
The alpha-ketoglutarate dehydrogenase complex of Escherichia coli utilizes pyruvate as a poor substrate, with an activity of 0.082 units/mg of protein compared with 22 units/mg of protein for alpha-ketoglutarate. Pyruvate fully reduces the FAD in the complex and both alpha-keto[5-14C]glutarate and [2-14C]pyruvate fully [14C] acylate the lipoyl groups with approximately 10 nmol of 14C/mg of protein, corresponding to 24 lipoyl groups. NADH-dependent succinylation by [4-14C]succinyl-CoA also labels the enzyme with approximately 10 nmol of 14C/mg of protein. Therefore, pyruvate is a true substrate. However, the pyruvate and alpha-ketoglutarate activities exhibit different thiamin pyrophosphate dependencies. Moreover, 3-fluoropyruvate inhibits the pyruvate activity of the complex without affecting the alpha-ketoglutarate activity, and 2-oxo-3-fluoroglutarate inhibits the alpha-ketoglutarate activity without affecting the pyruvate activity. 3-Fluoro[1,2-14C]pyruvate labels about 10% of the E1 components (alpha-ketoacid dehydrogenases). The dihydrolipoyl transsuccinylase-dihydrolipoyl dehydrogenase subcomplex (E2E3) is activated as a pyruvate dehydrogenase complex by addition of E. coli pyruvate dehydrogenase, the E1 component of the pyruvate dehydrogenase complex. All evidence indicates that the alpha-ketoglutarate dehydrogenase complex purified from E. coli is a hybrid complex containing pyruvate dehydrogenase (approximately 10%) and alpha-ketoglutarate dehydrogenase (approximately 90%) as its E1 components.
D000107:Acetylation; D004926:Escherichia coli / Q000201:enzymology*; D007655:Ketoglutarate Dehydrogenase Complex / Q000032:analysis*; D007656:Ketoglutaric Acids / Q000037:antagonists & inhibitors; D007658:Ketone Oxidoreductases / Q000032:analysis*; D010084:Oxidation-Reduction; D011768:Pyruvate Dehydrogenase Complex / Q000032:analysis*; D011773:Pyruvates / Q000037:antagonists & inhibitors / Q000378:metabolism; D019289:Pyruvic Acid; D013835:Thiamine Pyrophosphate / Q000494:pharmacology
D007656:Ketoglutaric Acids; D011768:Pyruvate Dehydrogenase Complex; D011773:Pyruvates; D019289:Pyruvic Acid; D007658:Ketone Oxidoreductases; D007655:Ketoglutarate Dehydrogenase Complex; D013835:Thiamine Pyrophosphate