漆树漆酶催化氧化对苯二胺反应的微量热法研究

STUDIES OF THE REACTION BETWEEN LACCASE AND p PHENYLENEDIAMIME BY MICROCALORIMETRY

在厌氧条件下，０．１ｍｏｌ／Ｌ的磷酸盐缓冲溶液（ｐＨ＝７．４）中，用微量热法测定了２９８．１５Ｋ时漆树漆酶与对苯二胺反应的摩尔反应焓ΔｒＨｍ＝－１６３．３６±０．３６ｋＪ／ｍｏｌ，米氏常数Ｋｍ＝５．５８×１０－３ｍｏｌ／Ｌ和表观一级反应速率常数ｋ１＝８．６３×１０－３ｓ－１，及此条件下用对苯二胺作底物时的漆酶活性值ＥＡ＝０．０４５ＩＵ．还利用阿伦尼乌斯经验公式计算了该反应的表观活化能，并讨论了酶－底复合过程的结合能ΔＧ０的计算．

The molar reation enthalpy,the Michaelis constant and the observed rate constant of the reaction between the Rhus vernicifera laccase and p phenylenediamine have been determined at 298.15 K by LKB 2107 microcalorimetry system in 0.1 mol/L phosphate salt buffer (pH7.4) to be ΔrH m=-136.36±0.36 kJ/mol, K m=5.58×10 -3 mol/L and k 1 =8.63×10 -3 s -1 , respectively.The catalyst activity of laccase with p phenylenediamine as substrate has been determined to be EA=0.045 IU in the experimental condition. The observed activation energy of non enzymic step of the reaction, the Gibbs binding energy of the combination process of laccase and substrate have been also calculated. The physical significance of the determined parameters were discussed for different step of the reaction.