有机溶剂中青霉素酰化酶催化的动力学与热力学

THE KINETICS AND THERMODYNAMICS OF PENICILLIN ACYLASE IN ORGANIC SOLVENTS

用电泳纯巨大芽孢杆菌胞外青霉素酸化酶，研究其在乙醇、正丙醇、异丙醇、正丁醇、丙酮、二氧六环、四氢呋喃等有机溶剂存在下的动力学和热力学特性，并与相应的溶液酶作比较，探讨溶剂酶（有机溶剂存在下的酶）和溶液酶在催化活性及分于构象方面的特性。

Penicillin acylase (EC, 3. 5. 1. 1. ) produced by B. megaterium was purified to electrophoretically homogeneous to investigate its kineticsand thermodynamics in the presence of such organic solvents as alcohol;1-propanol; 2-propanol; butanol; acetone; dioxane; tetrahydrofuran Theresults showed that Km of the enzyme obviously increased and kcat decreased with the decreasing of the dielectric constants of solvents. .However, the thermodynamic constants such as entropy (△S ), enthalpy (△H )and activation energy (E ) were significantly increased in organic solventscompsring with that in water. The results described above could be coneluded that the molecular conformation, at least a the actlve site of the enzyme, could be changed to be random in organic solvents and the combining site with the substrate of penicillin acylase would be at hydrophobio region.