ENZYMATIC CATALYSIS AND DYNAMICS IN LOW-WATER ENVIRONMENTS
ENZYMATIC CATALYSIS AND DYNAMICS IN LOW-WATER ENVIRONMENTS
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DOI：
10.1073/pnas.89.3.1100
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发表时间：
1992-02-01
影响因子：
11.1
通讯作者：
DORDICK, JS
中科院分区：
文献类型：
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作者：
AFFLECK, R;XU, ZF;DORDICK, JS
悬浮在有机溶剂中的酶代表了研究水参与酶结构和功能的多功能系统。向含有 1 M 1-丙醇的四氢呋喃中添加少于 1% (vol/vol) 的水会导致枯草杆菌蛋白酶 Carlsberg（来自地衣芽孢杆菌）的酯交换活性显着增加，这与活性位点极性的急剧增加以及活性位点内硝基氧自旋标记的旋转相关时间减少 90%（即迁移率增加）相关。超过 1% 的水对活性位点极性几乎没有额外影响，并且与自旋标记迁移率的进一步增加相一致，酯交换活性急剧下降。因此，酯交换活性随着酶水合和灵活性的增加而增加，然后减少（这可能是通过介电屏蔽耦合的），这表明部分水合的枯草杆菌蛋白酶的构象不同于几乎干燥的酶，即含水量低于 9% (wt/wt) 的酶。
Enzymes suspended in organic solvents represent a versatile system for studying the involvement of water in enzyme structure and function. Addition of less than 1% (vol/vol) water to tetrahydrofuran containing 1 M 1-propanol leads to a substantial increase in the transesterification activity of subtilisin Carlsberg (from Bacillus licheniformis) that correlates with a sharp increase in the active-site polarity and a 90% decrease in the rotational correlation time (i.e., increase in mobility) of a nitroxide spin label within the active site. Water in excess of 1 % has little additional effect on active-site polarity and coincides with a further increase in spin-label mobility, vet the transesterification activity decreases dramatically. Thus, transesterification activity increases and then decreases with increasing enzyme hydration and flexibility (which are presumable coupled through dielectric screening), suggesting that the conformation of partially hydrated subtilisin is different from that of the nearly dry enzyme-i.e., enzyme containing less than 9% (wt/wt) water.