Temperature dependence of mitochondrial oligomycin-sensitive proton transport ATPase |
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Authors: | G Solaini A Baracca G Parenti Castelli G Lenaz |
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Institution: | (1) Istituto di Chimica Biologica, Università di Bologna, Via Irnerio 48, Italy;(2) Istituto Botanico, Università di Bologna, Via Irnerio 42, Italy |
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Abstract: | The temperature dependence of the oligomycin-sensitive ATPase (complex V) kinetic parameters has been investigated in enzyme preparations of different phospholipid composition. In submitochondrial particles, isolated complex V, and complex V reconstituted in dimirystoyl lecithin vesicles, the Arrhenius plots show discontinuities in the range 18–28°C, while no discontinuity is detected with dioleoyl lecithin recombinant. Van't Hoff plots ofK
m
also show breaks in the same temperature interval, with the exception of the dioleoylenzyme vesicles, whereK
m
is unchanged. Thermodynamic analysis of the ATPase reaction shows that DMPC-complex V has rather larger values of activation enthalpy and activation entropy below the transition temperature (24°C) than those of the other preparations, while all enzyme preparations show similar free energies of activation (14.3–18.5 kcal/mol). The results indicate that temperature and lipid composition influence to a different extent both kinetic and thermodynamic parameters of ATP hydrolysis catalyzed by the mitochondrial ATPase. |
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Keywords: | OS-ATPase temperature effect kinetics lipid role membrane enzyme protein-lipid interaction (bovine mitochondria) |
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