微量热法研究过氧化氢酶反应

Microcalorimetry Applied to the Study of Catalase Reaction

利用微量热法和热动力学方程研究了过氢化氢酶反应。该反应遵循Ｍｉｃｈａｅｌｉｓ－Ｍｅｎｔｅｎ动力学，２９８．１５Ｋ和ｐＨ７．０时，其米氏常数、酶转换数以及摩尔反应焓分别为２．３６×１０－２ｍｏｌ／Ｌ、１．２０×１０４ｓ－１和－８３．６７ｋＪ·ｍｏｌ－１。过氧化氢酶反应后期对底物是一级反应，其总反应速度常数和一级速度常数分别为ｋｏ＝６．３１×１０５Ｌ·ｍｏｌ－１·ｓ－１和ｋ１＝６．３１×１０５／［Ｅｏ］ｓ－１。该反应服从Ｏｇｕｒａ机理，其酶－底物三元复合物的分解速度常数为６．００×１０３ｓ－１。

Microcalorimetry and thermokinetic equations were used to study H2O2 decomposition by beef liver catalase.The catalase reaction obeyed the Michaelis-Menten kinetics,and at 298.15 K and pH 7.0,the Michaelis constant (Km),the turnover number and the molar enthalpy(ΔrHm)of the reaction were 2.36×10-2 mol/L,1.20×104s-1 and-83.67 kJ·mol-1,respectively.The later period of catalase reaction was a first order reaction for H2O2,=6.31×105L·mol-1·s-1 and k1=6.31×10-5/[Eo]s-1,respectively.The catalase reaction obeyed Ogura mechanism,and the ternary complex decomposition rate constant was 6.00×103s-1.