水-乙醇混合溶剂中过氧化氢酶活性与构象的研究

Activity and Conformation of Catalase in Water - Ethanol Mixtures

用微量热法和荧光法分别测定了水-乙醇混合溶剂中过氧化氢酶活性与构象的变化.结果表明,随着乙醇浓度的增大,过氧化氢酶酶促反应的米氏常数K_m有所增大,而反应速率常数k_2及酶的催化活性则明显降低;336nm处的相对荧光强度不断增强,酶分子的构象发生了变化,其结构渐趋松散.乙醇对过氧化氢酶活性的影响乃是乙醇的竞争性抑制和溶剂效应引起的酶构象变化共同作用的结果.

The activity and conformation changes of catalase in water - ethanol mixtures were measured at 298.15K by means of microcalorimetry and fluorescence spectroscopy. The results showed that the Michaelis constant Km of catalase catalyzed reaction as well as the relative fluorescence intensity of catalase increased the rate constant k2 and the activity of catalase decreased with increasing the ethanol concentration. The conformation of catalase was changed with losing activity at the various concentration of ethanol. The lose of activity of catalase in water - ethanol mixtures was caused by the inhibition of ethanol and the conformational change of catalase.