Gupta M, Kale R K
Free Radical Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
Indian J Biochem Biophys. 1996 Oct;33(5):377-83.
The effect of Ca2+ on kinetics and thermodynamics of lipid peroxidation in microsomes prepared from liver of male Swiss albino mice (7-8 weeks old) was studied. Ca2+ was found to increase the Vmax in temperature dependent manner. Michaelis-Menten constant (Km) also increased with temperature. However, the linearity and extent of change in Km remained unaffected in presence of Ca2+, and was suggestive of non-competitive and mixed type of activation. The activation constant (Ka) obtained by the replotting of slopes of the Lineweaver-Burk plots against the reciprocal of Ca2+ concentration showed linear variation with temperature. The linear pattern of Arrhenius plots indicated non-involvement of parallel reactions of other intermediate species in the lipid peroxidation. Thermodynamic parameters delta H degree, delta S degree and delta G degree, associated with lipid peroxidation process were studied. The positive value of delta H degree is suggestive of the endothermic nature of the process. It appears that the NADPH induced lipid peroxidation is an entropy driven process.
研究了Ca2+对雄性瑞士白化小鼠（7-8周龄）肝脏制备的微粒体中脂质过氧化动力学和热力学的影响。发现Ca2+以温度依赖性方式增加Vmax。米氏常数（Km）也随温度升高而增加。然而，在Ca2+存在下，Km的线性和变化程度不受影响，提示为非竞争性和混合型激活。通过将Lineweaver-Burk图的斜率相对于Ca2+浓度的倒数重新绘制得到的激活常数（Ka）随温度呈线性变化。阿伦尼乌斯图的线性模式表明脂质过氧化过程中其他中间物种的平行反应未参与。研究了与脂质过氧化过程相关的热力学参数ΔH°、ΔS°和ΔG°。ΔH°的正值表明该过程为吸热性质。看来NADPH诱导的脂质过氧化是一个熵驱动的过程。
