Department of Chemical and Biochemical Engineering and Center for Biocatalysis and Bioprocessing, University of lowa, lowa City, lowa 52242, USA.
Biotechnol Bioeng. 1992 Feb 20;39(4):392-7. doi: 10.1002/bit.260390405.
Exchange of enzyme-bound H(2)O with T(2)O in aqueous solution followed by freeze drying provided tritiated water bound to chymotrypsin, subtilisin Carlsberg, and horseradish peroxidase. The desorption of T(2)O from these enzymes suspended in various organic solvents showed that all three enzymes lost enzyme-bound water with peroxidase losing the most T(2)O of the three in solvents of moderate to high polarity. Polar solvent resulted in the highest degree of T(2)O desorption (e.g., methanol desorbed from 56%-62% of the bound T(2)O), while nonpolar solvents resulted in the lowest degree of desorption (e.g., hexane desorbed from 0.4%-2% of the bound T(2)O). Desorption is nearly immediate with most of the desorbable T(2)O being released from the enzymes within the first 5 min. Both solvent dielectric and a measure of the saturated molar solubility of water in a given solvent provide accurate correlations between the properties of the organic solvents and the extent of T(2)O desorption. This investigation shows that water stripping from an enzyme into a nonaqueous medium does occur and can be significant in polar solvents.
在水溶液中，通过酶结合的 H(2)O 与 T(2)O 的交换，然后进行冷冻干燥，提供了与糜蛋白酶、枯草杆菌蛋白酶和辣根过氧化物酶结合的氚化水。将这些悬浮在各种有机溶剂中的酶解吸 T(2)O 的结果表明，这三种酶都失去了酶结合的水，而过氧化物酶在中等极性到高极性溶剂中失去的 T(2)O 最多。极性溶剂导致 T(2)O 的解吸程度最高（例如，甲醇从 56%-62%的结合 T(2)O 中解吸），而非极性溶剂导致的解吸程度最低（例如，正己烷从 0.4%-2%的结合 T(2)O 中解吸）。大多数可解吸的 T(2)O 在最初的 5 分钟内从酶中迅速释放出来。溶剂介电常数和给定溶剂中水中饱和摩尔溶解度的测量值为有机溶剂的性质与 T(2)O 解吸程度之间提供了准确的相关性。这项研究表明，水从酶中脱除到非水介质中确实会发生，并且在极性溶剂中可能会很显著。
