Wharton D C, Gibson Q H
Biochim Biophys Acta. 1976 Jun 8;430(3):445-53. doi: 10.1016/0005-2728(76)90020-7.
The reaction between a cytochrome oxidase from Pseudomonas aeruginosa and oxygen has been studied by a rapid mixing technique. The data indicate that the heme d1 moiety of the ascorbate-reduced enzyme is oxidized faster than the heme c component. The oxidation of heme d1 is accurately second order with respect to oxygen and has a rate constant of 5.7 - 10(4) M-1 - s-1 at 20 degrees C. The oxidation of the heme c has a first order rate constant of about 8 s-1 at infinite concentration of O2. The results indicate that the rate-limiting step is the internal transfer of electrons from heme c to heme d1. These more rapid reactions are followed by more complicated but smaller abcorbance changes whose origin is still not clear. The reaction of ascorbate-reduced oxidase with CO has also been studied and is second order with a rate constant of 1.8 - 10(4) M-1 - s-1. The initial reaction with CO is followed by a slower reaction of significantly less magnitude. The equilibrium constant for the reaction with CO, calculated as a dissociation constant from titrimetric experiments with dithionite-reduced oxidase, is about 2.3 - 10(-6) M. From these data a rate constant of 0.041 s-1 can be calculated for the dissociation of CO from the enzyme.
利用快速混合技术研究了铜绿假单胞菌细胞色素氧化酶与氧气之间的反应。数据表明，抗坏血酸还原酶的血红素d1部分比血红素c成分氧化得更快。血红素d1的氧化相对于氧气而言准确地为二级反应，在20℃时速率常数为5.7 - 10(4) M-1 - s-1。在氧气浓度无限大时，血红素c的氧化一级速率常数约为8 s-1。结果表明，限速步骤是电子从血红素c到血红素d1的内部转移。这些更快的反应之后是更复杂但变化较小的吸光度变化，其来源尚不清楚。还研究了抗坏血酸还原氧化酶与CO的反应，该反应为二级反应，速率常数为1.8 - 10(4) M-1 - s-1。与CO的初始反应之后是一个幅度明显较小的较慢反应。用连二亚硫酸盐还原氧化酶通过滴定实验计算得出的与CO反应的平衡常数，以解离常数计约为2.3 - 10(-6) M。根据这些数据，可以计算出CO从酶上解离的速率常数为0.041 s-1。
