title: ATP inhibition competes with activating cations in modulating the NAD(P)(+)-malic enzyme activity in the mitochondrial matrix of Xenopus laevis oocytes.
abstract: 1. ATP inhibits NAD(P)(+)-dependent malic enzyme activity by competing with the essential activators Mn2+ and Mg2+. 2. The kinetics fit an equation of co-operative kind with Ki of 26 microM and KA of 11.3 microM for ATP/Mn2+ competition; with Ki of 1.1 mM and KA of 0.96 mM for ATP/Mg2+ competition. 3. In the absence of the inhibitor, the co-operativity index increases from 1.77 to greater than 4 in the presence of ATP, in the case of ATP/Mn2+ competition, while it increases from 1.88 to greater than 9 for ATP/Mg2+ competition.
authors.affiliation: Department of Cell Biology and Physiology, University of L'Aquila, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Petrucci
authors.forename: P
authors.initials: P
authors.lastname: Cesare
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D008274:Magnesium / Q000494:pharmacology*; D008291:Malate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008345:Manganese / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D009865:Oocytes / Q000187:drug effects / Q000201:enzymology*; D014982:Xenopus laevis
chemical_list: D008345:Manganese; D000255:Adenosine Triphosphate; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+); D008274:Magnesium