Temperature dependence of the barley root plasma membrane-bound Ca2+- and Mg2+-dependent ATPase

摘要: Arrhenius plots of the maximal velocities for Ca2+-and Mg2+-dependent ATPase activities found in a plasma membrane-rich microsome fraction isolated from roots barley (Hordeum vulgare L. cv. Conquest) were nonlinear. plot analyses using relation which produced curvilinear accurately fit data and allowed calculation activation enthalpies molar heat capacities activation. The temperature dependence computed Km values Ca2+- was complex, with highest enzyme-substrate affinities being obtained near seedling growth (16°C). Using electron paramagnetic resonance spectroscopy amphiphilic cationic anionic spin probes, it possible to demonstrate that changes increasing Ca2+ concentrations could alter mobility membrane lipid polar head groups. Inhibition by high levels may result Ca2+-induced reduction group mobility. role group-protein interactions complex root kinetic constants is discussed.