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用LKB-2107型微量热系统,测定了漆酶催化氧化3,4-二羟基苯甲醛、邻甲氧基酚、邻苯三酚、3,4,5-三羟基本甲酸反应的热谱图,利用热谱图计算了米氏常数(K_m)、反应速率常数(k_2)和热力学参数(Δ_rH_m,ΔG_0,ΔG_T~≠,E_a,ΔS_T~≠).并应用过渡态理论对其催化过程进行了分析.结果表明:稳定过渡态结构有利于酶促反应,酶-底物在反应物时相互作用仅仅是降低酶的催化效率.提出两种可能提高酶催化效率的方法.由活化熵(ΔS_T)<0得出酶-底物在过渡态的结构较酶-底物复合物的结构更为有序.
LKB-2107 trace calorimetry system was used to determine the thermograms of laccase catalyzed oxidation of 3,4-dihydroxybenzaldehyde, o-methoxy phenol, pyrogallol, and 3,4,5-trihydroxybenzoic acid (K_m), reaction rate constant (k_2) and thermodynamic parameters (Δ_rH_m, ΔG_0, ΔG_T ~ ≠, E_a, ΔS_T ~ ≠) were calculated by using the thermogram. The catalytic process was also carried out using the transition state theory The results showed that the stable transition state structure was favorable to the enzymatic reaction and the interaction between the enzyme and the substrate was only the decrease of the catalytic efficiency of the enzyme. Two methods were proposed to improve the catalytic efficiency of the enzyme. The activation entropy (ΔS_T) <0 shows that the structure of the enzyme-substrate in the transition state is more ordered than that of the enzyme-substrate complex.