Urea-induced Inactivation and Unfolding of Recombinant Phospholipid Hydroperoxide Glutathione Peroxidase from Oryza sativa  

作　　者：WANG Feng ZHOU Hui-ping KONG Bao-hua FAN Jing-hua CHEN Hai-ru LIU Jin-yuan 

机构地区：[1]Key Laboratory of Molecular Biology and Protein Science of Ministry of Education, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, P. R. China [2]Key Laboratory for Plant Pathology of Yunnan Province, Yunnan Agricultural University, Kunming 650201, P. R. China

出　　处：《Chemical Research in Chinese Universities》2007年第5期562-566,共5页高等学校化学研究（英文版）

基　　金：Supported by the National Basic Research Program of China(No.2006CB101706);the Hi-tech Research and DevelopmentProgram of China(No.2007AA100604);the National Natural Science Foundation of China(Nos.30170080and39770078).

摘　　要：Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst the glutathione peroxidases.In this study,urea-induced effects on the inactivation and unfolding of a recombinant phospholipid hydroperoxide glutathione peroxidase（PHGPx）from Oryza sativa were investigated by means of circular dichroism and fluorescence spectroscopy.With the increase of urea concentration,the residual activity of OsPHGPx decreases correspondingly.When the urea concentration is above 5.0 mol/L,there was no residual activity.In addition,the observed changes in intrinsic tryptophan fluorescence,the binding of the hydrophobic fluorescence probe ANS,and the far UV CD describe a common dependence on the concentration of urea suggesting that the conformational features of the native OsPHGPx are lost in a highly cooperative single transition.The unfolding process comprises of three zones：the native base-line zone between 0 and 2.5 mol/L urea,the transition zone between 2.5 and 5.5 mol/L urea,and the denatured base-line zone above 5.5 mol/L urea.The transition zone has a midpoint at about 4.0 mol/L urea.Phospholipid hydroperoxide glutathione peroxidase is an antioxidant enzyme that has the highest capability of reducing membrane-bound hydroperoxy lipids as compared to free organic and inorganic hydroperoxides amongst the glutathione peroxidases.In this study,urea-induced effects on the inactivation and unfolding of a recombinant phospholipid hydroperoxide glutathione peroxidase（PHGPx）from Oryza sativa were investigated by means of circular dichroism and fluorescence spectroscopy.With the increase of urea concentration,the residual activity of OsPHGPx decreases correspondingly.When the urea concentration is above 5.0 mol/L,there was no residual activity.In addition,the observed changes in intrinsic tryptophan fluorescence,the binding of the hydrophobic fluorescence probe ANS,and the far UV CD describe a common dependence on the concentration of urea suggesting that the conformational features of the native OsPHGPx are lost in a highly cooperative single transition.The unfolding process comprises of three zones：the native base-line zone between 0 and 2.5 mol/L urea,the transition zone between 2.5 and 5.5 mol/L urea,and the denatured base-line zone above 5.5 mol/L urea.The transition zone has a midpoint at about 4.0 mol/L urea.

关 键 词：Circular dichroism Fluorescence Conformational change Phospholipid hydroperoxide glutathione peroxidase（PHGPx） Urea titration 

分 类 号：Q55[生物学—生物化学]