Department of Chemistry, University of Modena and Reggio Emilia, Via Campi 183, I-41125 Modena, Italy.
Langmuir. 2011 Sep 6;27(17):10683-90. doi: 10.1021/la201876k. Epub 2011 Aug 11.
The peroxidase activity of wild-type yeast cytochrome c and its triple mutant K72AK73AK79A adsorbed onto kaolinite was investigated as a function of pH and temperature. Both adsorbed proteins displayed an appreciable catalytic activity, which remained constant from pH 7 to pH 10, decreased below pH 7, and showed a remarkable increase at pH values lower than 4. In the whole pH range investigated the catalytic activity of the adsorbed wild-type cytochrome c was higher than that of the mutant. Both diffuse-reflectance UV-vis and resonance Raman spectroscopies applied on solid samples were used to probe the structural features responsible for the catalytic activity of the immobilized proteins. At neutral and alkaline pH values a six-coordinate low-spin form of cytochrome c was observed, while at pH < 7 the formation of a high-spin species occurred whose population increased at decreasing pH. The orientation and exposure of the heme to the substrate-strictly dependent on adsorption-was found to affect the peroxidase activity.
研究了野生型酵母细胞色素 c 和其三重突变体 K72AK73AK79A 在高岭土上吸附后的过氧化物酶活性与 pH 值和温度的关系。两种吸附蛋白均表现出相当大的催化活性，在 pH7 到 pH10 之间保持不变，低于 pH7 时降低，低于 4 时显著增加。在所研究的整个 pH 范围内，吸附的野生型细胞色素 c 的催化活性高于突变体。应用于固态样品的漫反射紫外可见光谱和共振拉曼光谱均用于探测对固定化蛋白的催化活性有影响的结构特征。在中性和碱性 pH 值下，观察到细胞色素 c 的六配位低自旋形式，而在 pH < 7 时，形成了一种高自旋物种，其数量随着 pH 的降低而增加。发现血红素的取向和暴露（吸附依赖性很强）会影响过氧化物酶的活性。
