Erman J E
Biochim Biophys Acta. 1975 Jul 27;397(1):36-42. doi: 10.1016/0005-2744(75)90176-x.
The apparent bimolecular rate constant for the oxidation of dicyano-bis(1,10 phenanthroline) iron(II) by compound II of cytochrome c peroxidase (ferrocytochrome c; hydrogen-peroxide oxidoreductase EC 1.11.1.5) has been measured over the pH range 2.5-11.0 at 0.1 M ionic strength, 25 degrees C, by the stopped-flow technique. An ionizable group in the enzyme, with a pKa of 4.5, strongly influences the electron transfer rate between the ferrous complex and the oxidized site in the enzyme. The electron transfer is fastest when the group is protonated, with a rate constant of 2.9 - 10-5 M--1 - s-1. The rate constantdecreases over three orders of magnitude when the proton dissociates. The apparent bimolecular rate constant for the oxidation of the ferrous complex by compound I of cytochrome c peroxidase was determined between pH 3.5 and 6. Under all conditions where this rate constant could be measured it was about three times larger than that for the oxidation by compound II.
在0.1 M离子强度、25℃条件下，采用停流技术，在pH值2.5 - 11.0范围内测定了细胞色素c过氧化物酶（亚铁细胞色素c；过氧化氢氧化还原酶，EC 1.11.1.5）的化合物II氧化二氰基双（1,10-菲咯啉）铁（II）的表观双分子速率常数。酶中一个pKa为4.5的可电离基团强烈影响亚铁配合物与酶中氧化位点之间的电子转移速率。当该基团质子化时，电子转移最快，速率常数为2.9×10⁻⁵ M⁻¹·s⁻¹。当质子解离时，速率常数下降三个数量级以上。在pH 3.5至6之间测定了细胞色素c过氧化物酶的化合物I氧化亚铁配合物的表观双分子速率常数。在所有能测量该速率常数的条件下，其值约为化合物II氧化速率常数的三倍。
