非离子表面活性剂水溶液中木素过氧化物酶催化氧化藜芦醇反应稳态动力学研究

Steady - state Kinetic Studies on the Oxidation of Veratryl Alcohol Catalyzed by Ligninase in Aqueous Media Containing Nonionic Surfactant

研究表面活性剂缔合体系中木素模型化合物的生物降解机制具有重要意义.本文以黄孢原毛平革菌在一定条件下分泌出的木素过氧化物酶(LiP)为生物催化剂,用分光光度技术研究了非离子表面活性剂TritonX-100存在下水溶液中LiP催化氧化藜芦醇(VA)反应的动力学.结果表明,在TritonX-100水溶液中,LiP催化氧化VA反应遵循乒乓机制.稳态动力学参数测定表明,TritonX-100对上述酶促反应的最大反应初速率及VA的米氏常数影响不大.但使过氧化氢的米氏常数下降近50%.依据不同TritonX-100浓度下(远低于、接近于和远大于其临界胶束浓度)酶促反应的动力学参数和VA的疏水性指数,我们认为该结果是表面活性剂单体对酶蛋白分子的修饰所致.

Biodegradation of lignin model compounds is of great significance to the world's environment and resources. Phanerochaete chrysosporium, a wood - decaying fungus, produces extracellular enzymic proteins which are able to catalyze the oxidation of a large variety of substrates through the reaction with hydrogen peroxide. In this paper, ligninase (UP) and its optimum substrate veratryl alcohol (VA) are selected. The kinetics of the H2O2 - dependent ligninase - catalyzed oxidation of veratryl alcohol in the aqueous medium containing nonionic surfactant TritonX - 100 has been investigated using spectrophotometric technique. The results obtained based on steady - state kinetic studies suggest a ping - pong mechanism. Presence of TritonX - 100 has small effect on the maximum initial rate and the Michaelis constant for VA, but it causes the Michaelis constant for H2O2 to decrease dramatically. Based on the kinetic parameters of the enzyme catalyzed reaction at different TritonX - 100 concentrations (lower than, near to, and larger than its critical micelle concentration) and the hydrophobicity index of VA, we think that modification of the enzymic protein by the surfactant monomer is responsible for the above - mentioned results.