1. The binding of Ca2+ ions to purified pig heart NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase, freed of contaminating Ca2+ by parvalbumin/polyacrylamide chromatography, has been studied by flow dialysis and by the use of fura-2. 2. For the 2-oxoglutarate dehydrogenase complex, 3.5 mol of Ca2+-binding sites/mol of complex were apparent, with an apparent dissociation constant (Kd value) for Ca2+ of 2.0 microM. These values were little affected by Mg2+ ions, ADP or 2-oxoglutarate. 3. By contrast, binding of Ca2+ to NAD+-isocitrate dehydrogenase (Kd = 14 microM) required ADP, isocitrate and Mg2+ ions. The number of Ca2+-binding sites associated with NAD+-isocitrate dehydrogenase was then 0.9 mol/mol of tetrameric enzyme. 4. The 2-oxoglutarate dehydrogenase complex bound ADP (as ADP3-) to a group of tight-binding sites (Kd = 3.1 microM) with a stoichiometry, 3.3 mol/mol of complex, similar to that for the binding of Ca2+; a variable number of much weaker sites (Kd = 100 microM) for ADP3- was also apparent.
Research Article|October 15 1989
The binding of Ca2+ ions to pig heart NAD+-isocitrate dehydrogenase and the 2-oxoglutarate dehydrogenase complex
G A Rutter;
Biochem J (1989) 263 (2): 453-462.
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G A Rutter, R M Denton; The binding of Ca2+ ions to pig heart NAD+-isocitrate dehydrogenase and the 2-oxoglutarate dehydrogenase complex. Biochem J 15 October 1989; 263 (2): 453–462. doi: https://doi.org/10.1042/bj2630453
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