title: Lipid protein interactions in mitochondria. VII. A comparison of the effects of lipid removal and lipid perturbation of the kinetic properties of mitochondrial ATPase.
abstract: We investigated the kinetics of mitochondrial ATPase in bovine heart mitochondria and submitochondrial particles upon treatment with phospholipase A2, or upon addition of n-butanol to perturb the lipid protein interactions. The changes observed are the following: (1) Lipid removal or perturbation with butanol is accompanied by loss of ATPase activity with decrease of both V and of the KM for ATP. (2) There are changes of activation energy of ATPase activity at temperatures above the discontinuity normally observed for membrane-bound enzymes in mitochondria. In particular, butanol abolishes the discontinuity, and induces a constant activation energy of about 32 kcal/mol in the range 8--37 degrees C. (3) Butanol modifies the pH dependence of ATPase shifting the pH optimum from around 10 to less alkaline values. The optimum for Mg2+ concentrations is increased by the solvent. (4) Treatment with phospholipase A2 results in a removal of oligomycin-sensitive ATPase, whereas butanol addition prevents oligomycin inhibition of ATPase. (5) In beef heart mitochondria, a spin-labelled analog of the inhibitor, dicyclohexyl carbodiimide, did not show any change in environment upon butanol addition, unlike that found in mitochondria from Saccharomyces cerevisiae.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D000440:Butanols / Q000494:pharmacology; D002417:Cattle; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008928:Mitochondria / Q000201:enzymology*; D008929:Mitochondria, Heart / Q000187:drug effects / Q000201:enzymology*; D009840:Oligomycins / Q000494:pharmacology; D010740:Phospholipases; D010743:Phospholipids / Q000502:physiology*; D013367:Submitochondrial Particles / Q000187:drug effects / Q000201:enzymology*; D013816:Thermodynamics
chemical_list: D000440:Butanols; D009840:Oligomycins; D010743:Phospholipids; D010740:Phospholipases; D000251:Adenosine Triphosphatases; D008274:Magnesium