Alkaline unfolding and salt-induced folding of bovine liver catalase at high pH.
Alkaline unfolding and salt-induced folding of bovine liver catalase at high pH.
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高 pH 条件下牛肝过氧化氢酶的碱性解折叠和盐诱导折叠。
DOI：
10.1046/j.1432-1327.1998.2550178.x
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
S. K. Jain
中科院分区：
文献类型：
--
作者：
Shashi Prajapati;V. Bhakuni;K. R. Babu;S. K. Jain
我们已经研究了牛肝过氧化氢酶的碱性去折叠和它对离子强度的依赖性，通过酶活性测量和组合的光学方法，如圆二色谱，荧光和吸收光谱。在高pH（11.5）和低离子强度的条件下，天然四聚体酶解离成单体，酶活性完全丧失，α-螺旋含量显著丧失。增加离子强度通过添加盐，如氯化钾和硫酸钠导致折叠的碱性展开酶的单体的关联四聚体，但与天然酶相比，具有显着不同的结构特性。与天然酶相比，盐诱导的四聚体中间体的特征在于掩埋的疏水簇的显著暴露和显著降低的α-螺旋含量。重折叠/重建的研究表明，盐诱导的部分折叠的四聚体中间体显示出显着更高的效率相比，碱性变性过氧化氢酶在盐的情况下的重折叠/重建。这些研究表明，折叠的多聚体酶的收益可能是通过疏水崩溃的部分折叠的多聚体中间与暴露的疏水簇。
We have studied the alkaline unfolding of bovine liver catalase and its dependence on ionic strength by enzymic activity measurements and a combination of optical methods like circular dichroism, fluorescence and absorption spectroscopies. Under conditions of high pH (11.5) and low ionic strength, the native tetrameric enzyme dissociates into monomers with complete loss of enzymic activity and a significant loss of alpha-helical content. Increase in ionic strength by addition of salts like potassium chloride and sodium sulphate resulted in folding of alkaline-unfolded enzyme by association of monomers to tetramer but with significantly different structural properties compared to native enzyme. The salt-induced tetrameric intermediate is characterized by a significant exposure of the buried hydrophobic clusters and significantly reduced alpha-helical content compared to the native enzyme. The refolding/reconstitution studies showed that the salt-induced partially folded tetrameric intermediate shows significantly higher efficiency of refolding/reconstitution as compared to alkaline-denatured catalase in the absence of salts. These studies suggest that folding of multimeric enzymes proceeds probably through the hydrophobic collapse of partially folded multimeric intermediate with exposed hydrophobic clusters.