亚铬离子还原金属蛋白的动力学（漆酶 - 细胞色素c - 质体蓝素 - 温度 - 速率常数）
Kinetics of the reduction of metalloproteins by chromous ion (laccase-cytochrome c-plastocyanins-temperature-rate constants).
作者信息
Dawson J W, Gray H B, Holwerda R A, Westhead E W
出版信息
Proc Natl Acad Sci U S A. 1972 Jan;69(1):30-3. doi: 10.1073/pnas.69.1.30.
The reduction of Cu(330) in Rhus vernicifera laccase by chromous ion is 30% faster than reduction of Cu(614) at room temperature [pH 4.8, mu = 0.1 (NaCl)], and two parallel first-order paths, attributed to heterogeneity of the protein, are observed at both wavelengths. The reactions of stellacyanin, spinach and French-bean plastocyanins, and cytochrome c with chromous ion under similar conditions are faster than that with laccase by factors of 10(2) to 10(4), and are first order in protein concentration. Comparison of rates and activation parameters for the reduction of "blue" copper in laccase, stellacyanin, and the two plastocyanins indicates that reduction of the Cu(614) site in laccase may occur by intramolecular electron transfer from one of the Cu(330) sites. Our value of DeltaHdouble dagger (17.4 kcal/mol) for the chromous ion reduction of cytochrome c is consistent with a mechanism in which major conformational changes in the protein must accompany electron transfer.
在室温下[pH 4.8，μ = 0.1（NaCl）]，铬离子对漆树漆酶中Cu(330)的还原速度比Cu(614)的还原速度快30%，并且在两个波长处均观察到两条平行的一级反应路径，这归因于蛋白质的不均一性。在相似条件下，紫铜蓝蛋白、菠菜和菜豆质体蓝素以及细胞色素c与铬离子的反应比与漆酶的反应快10²到10⁴倍，并且对蛋白质浓度呈一级反应。漆酶、紫铜蓝蛋白以及两种质体蓝素中“蓝色”铜还原反应的速率和活化参数比较表明，漆酶中Cu(614)位点的还原可能通过分子内电子从一个Cu(330)位点转移而发生。我们测得的细胞色素c被铬离子还原的ΔH‡值（17.4千卡/摩尔）与一种机制相符，即蛋白质中的主要构象变化必定伴随电子转移。
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