Rodakiewicz-Nowak Janina, Ito Masaaki
Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, 30 239 Kraków, Poland.
J Colloid Interface Sci. 2005 Apr 15;284(2):674-9. doi: 10.1016/j.jcis.2004.10.052.
The effect of AOT (sodium-bis(2-ethylhexyl sulfosuccinate)) on enzymatic activity of the organic solvent resistant tyrosinase (OSRT) in aqueous phosphate buffer solutions and in water-in-oil microemulsions of the water/AOT/isooctane system has been investigated. In contrast to mushroom tyrosinase, AOT does not activate OSRT in aqueous solutions, altering its activity very little at concentrations lower than 2 mM. Increasing contents of AOT in isooctane reduce the observed initial reaction rates of oxidation of t-butylcatechol (tBC) and 4-methylcatechol (4-MC). Similarly to mushroom tyrosinase, the effect has been described using an equation based on preferential binding of the substrates by surfactant interface layers. The apparent Michaelis-Menten substrate binding constants increase linearly with AOT concentration (with slopes of 0.12+/-0.02 and 0.051+/-0.006 for tBC and 4-MC, respectively), and the effective enzyme turnover number in the microemulsions remains practically constant.
研究了双（2-乙基己基）磺基琥珀酸钠（AOT）对耐有机溶剂酪氨酸酶（OSRT）在磷酸盐水溶液以及水/AOT/异辛烷体系的油包水微乳液中的酶活性的影响。与蘑菇酪氨酸酶不同，AOT在水溶液中不会激活OSRT，在浓度低于2 mM时对其活性影响很小。异辛烷中AOT含量的增加会降低观察到的叔丁基邻苯二酚（tBC）和4-甲基邻苯二酚（4-MC）氧化的初始反应速率。与蘑菇酪氨酸酶类似，该效应已通过基于表面活性剂界面层对底物的优先结合的方程进行了描述。表观米氏底物结合常数随AOT浓度线性增加（tBC和4-MC的斜率分别为0.12±0.02和0.051±0.006），并且微乳液中的有效酶周转数实际上保持恒定。
