核糖核酸酶A在丁酸十二铵-环己烷反胶束溶液中的催化动力学

Kinetics of Catalysis by Ribonuclease A in Reverse Micelles Formed by Dodecylammonium Butyrate and Water in Cyclohexane

研究了核糖核酸酶Ａ（ＲＮａｓｅＡ）在丁酸十二铵（ＤＡＢ）－环己烷反胶束溶液中催化水解胞苷２，３－环单磷酸酯的动力学，数据符合Ｍｉｃｈａｅｌｉｓ－Ｍｅｎｔｅｎ酶催化机理．以ｋｃａｔ／Ｋｍ表示酶催化活性时，ＲＮａｓｅＡ在反胶束溶液中的催化活性是在水溶液中的１４～３０倍．无论是固定ＤＡＢ浓度还是固定Ｈ２Ｏ与ＤＡＢ浓度之比，随增溶水量的增加，ｋｃａｔ／Ｋｍ呈下降趋势．

The kinetics of hydrolysis of cytidine 2,3 cyclic phosphate(CP) catalyzed by ribonuclease A(RNase A) solubilized in reverse micelles formed by dodecylammonium butyrate(DAB) in cyclohexane has been investigated. The results show that the Michaelis Menten law can be applied to DAB cyclohexane reverse micellar solutions as well as to aqueous solutions. The enzyme efficiency(expressed in terms of the ratio k cat / K m) of RNase A solubilized in DAB cyclohexane reverse micellar solutions is 14 30 times of that in aqueous solution. Under the conditions at constant concentration of DAB as well as at constant molecular ratio of H 2O and DAB, the enzymetic activity of RNase A in reverse micellar solutions decreases as the water content is increased. The results were explained briefly in terms of the changes in the conformation of the enzyme as well as in the concentrations of the enzyme and the substrate in inner water phase.