Institute of Analytical Chemistry, University of Copenhagen, Copenhagen, Denmark.
FEBS J. 2011 Sep;278(18):3463-71. doi: 10.1111/j.1742-4658.2011.08268.x. Epub 2011 Aug 31.
Rate constants and activation parameters have been determined for the internal electron transfer from type 1 (T1) to type 3 (T3) copper ions in laccase from both the fungus Trametes hirsuta and the lacquer tree Rhus vernicifera, using the pulse radiolysis method. The rate constant at 298 K and the enthalpy and entropy of activation were 25 ± 1 s(-1), 39.7 ± 5.0 kJ·mol(-1) and -87 ± 9 J·mol(-1) ·K(-1) for the fungal enzyme and 1.1 ± 0.1 s(-1), 9.8 ± 0.2 kJ·mol(-1) and -211 ± 3 J·mol(-1) ·K(-1) for the tree enzyme. The initial reduction of the T1 site by pulse radiolytically produced radicals was direct in the case of T. hirsuta laccase, but occured indirectly via a disulfide radical in R. vernicifera. The equilibrium constant that characterizes the electron transfer from T1 to T3 copper ions was 0.4 for T. hirsuta laccase and 1.5 for R. vernicifera laccase, leading to full reduction of the T1 site occurring at 2.9 ± 0.2 electron equivalents for T. hirsuta and 4 electron equivalents for R. vernicifera laccase. These results were compared with each other and with those for the same process in other multicopper oxidases, ascorbate oxidase and Streptomyces coelicolor laccase, using available structural information and electron transfer theory.
使用脉冲辐射法测定了来自糙皮侧耳（Trametes hirsuta）真菌和漆树（Rhus vernicifera）的漆酶中 1 型（T1）到 3 型（T3）铜离子内部电子转移的速率常数和活化参数。在 298 K 时的速率常数、活化焓和熵分别为 25 ± 1 s(-1)、39.7 ± 5.0 kJ·mol(-1) 和-87 ± 9 J·mol(-1)·K(-1)，真菌酶的速率常数为 1.1 ± 0.1 s(-1)、9.8 ± 0.2 kJ·mol(-1) 和-211 ± 3 J·mol(-1)·K(-1)，树酶的速率常数为 1.1 ± 0.1 s(-1)、9.8 ± 0.2 kJ·mol(-1) 和-211 ± 3 J·mol(-1)·K(-1)。T. hirsuta 漆酶中 T1 部位的初始还原是通过脉冲辐射产生的自由基直接进行的，而 R. vernicifera 中的还原则是通过二硫自由基间接进行的。T1 到 T3 铜离子的电子转移的特征平衡常数对于 T. hirsuta 漆酶为 0.4，对于 R. vernicifera 漆酶为 1.5，这导致 T1 部位的完全还原发生在 T. hirsuta 为 2.9 ± 0.2 电子当量，R. vernicifera 为 4 电子当量。将这些结果与其他多铜氧化酶、抗坏血酸氧化酶和链霉菌（Streptomyces coelicolor）漆酶的相同过程的结果进行了比较，并使用了可用的结构信息和电子转移理论。
