Bashford C L, Prince R C, Takamiya K I, Dutton P L
Biochim Biophys Acta. 1979 Feb 8;545(2):223-35. doi: 10.1016/0005-2728(79)90202-0.
The reductant of ferricytochrome c2 in Rhodopseudomonas sphaeroides is a component, Z, which has an equilibrium oxidation-reduction reaction involving two electrons and two protons with a midpoint potential of 155 mV at pH 7. Under energy coupled conditions, the reduction of ferricytochrome c2 by ZH2 is obligatorily coupled to an apparently electrogenic reaction which is monitored by a red shift of the endogeneous carotenoids. Both ferricytochrome c2 reduction and the associated carotenoid bandshift are similarly affected by the concentrations of ZH2 and ferricytochrome c2, pH, temperature the inhibitors diphenylamine and antimycin, and the presence of ubiquinone. The second-order rate constant for ferricytochrome c2 reduction at pH 7.0 and at 24 degrees C was 2 - 10(9) M-1 - s-1, but this varied with pH, being 5.1 - 10(8) M-1 = s-1 at pH 5.2 and 4.3 - 10(9) M-1 - s-1 at pH 9.3. At pH 7 the reaction had an activation energy of 10.3 kcal/mol.
球形红假单胞菌中细胞色素c2的还原剂是一种组分Z，它具有涉及两个电子和两个质子的氧化还原平衡反应，在pH 7时中点电位为155 mV。在能量偶联条件下，ZH2对细胞色素c2的还原必然与一个明显的电致反应偶联，该电致反应通过内源性类胡萝卜素的红移来监测。细胞色素c2的还原以及相关的类胡萝卜素带移同样受到ZH2和细胞色素c2的浓度、pH、温度、抑制剂二苯胺和抗霉素以及泛醌的存在的影响。在pH 7.0和24℃下细胞色素c2还原的二级速率常数为2×10⁹ M⁻¹·s⁻¹，但这随pH而变化，在pH 5.2时为5.1×10⁸ M⁻¹·s⁻¹，在pH 9.3时为4.3×10⁹ M⁻¹·s⁻¹。在pH 7时，该反应的活化能为10.3 kcal/mol。
