title: [Kinetic properties of NADP-specific isocitrate dehydrogenase from bovine adrenals].
abstract: At low concentrations of Mg2+ or Mn2+ the reaction catalyzed by isocitrate dehydrogenase from bovine adrenal cortex proceeds with a lag period which disappears as a result of the enzyme saturation with Mn2+ or Mg2+. The nu o versus D,L-isocitrate concentration curve is non-hyperbolic, which may be interpreted either by the presence of two active sites with different affinity for the substrate (K'mapp = 2.3 and 63 microM) within the enzyme molecule or by the "negative" cooperativity of these sites. The apparent Km value for NADP lies within the range of 3.6-9 microM. High concentrations of NADP inhibit isocitrate dehydrogenase (Ki = 1.3 mM). NADP.H inhibits the enzyme in a mixed manner with respect to NADP (Ki = 0.32 mM). In the presence of NADP.H the curve nu o dependence on NADP concentration shows a "negative" cooperativity between NADP binding sites. The reverse enzyme-catalyzed reaction of reductive carboxylation of 2-oxoglutarate does not exhibit any significant deviations from the Michaelis-Menten kinetics. The Km value for 2-oxoglutarate is 120 microM, while that for NADP.H is 10 microM.
mesh_terms: D000311:Adrenal Glands / Q000201:enzymology*; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D004492:Edetic Acid / Q000494:pharmacology; D007521:Isocitrate Dehydrogenase / Q000378:metabolism*; D007700:Kinetics; D009249:NADP / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D009249:NADP; D004492:Edetic Acid; D007521:Isocitrate Dehydrogenase; C039355:isocitrate dehydrogenase (NADP+)
vernacular_title: Kineticheskie svoĭstva NADP-spetsifichnoĭ izotsitratdegidrogenazy iz nadpochechnikov byka.