Influence of Ca2+ on kinetics and thermodynamics of the NADPH-dependent microsomal lipid peroxidation.
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.
Gupta
M
M
Free Radical Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.
Kale
R K
RK
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects*; D008297:Male; D051379:Mice; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D013816:Thermodynamics
D009249:NADP; D009251:NADPH-Ferrihemoprotein Reductase; D002118:Calcium