Moody A J, Richardson M, Spencer J P, Brandt U, Rich P R
Glynn Research Institute, Bodmin, U.K.
Biochem J. 1994 Sep 15;302 ( Pt 3)(Pt 3):821-6. doi: 10.1042/bj3020821.
A form of fully oxidized bovine heart cytochrome c oxidase that is induced by CO2/HCO3- is described. The ligand-binding properties of this form are similar to those of Cl(-)-ligated oxidase [Moody, Cooper and Rich (1991) Biochim. Biophys. Acta 1059, 189-207]. Both bind cyanide at a rate (0.2 M-1.s-1 at pH 6.5) intermediate between the rate of binding to the fast and slow forms of the enzyme, and binding of formate to both is almost undetectable. They are also similar in showing poor reactivity with H2O2, or with CO in the presence of O2, which, with fast oxidase, induce the formation of the 'ferryl' and 'peroxy' states respectively. However, there is a clear difference in the near-u.v./visible absorption spectra of the two forms; that induced by CO2/HCO3- has a Soret maximum at 427 nm whereas Cl(-)-ligated oxidase has a Soret maximum similar to that of fast oxidase at about 424 nm. It appears that both CO2/HCO3- and Cl- are members of a class of ligands that lowers the reactivity of the binuclear centre but does not impede intramolecular electron transfer from haem a to the binuclear centre, unlike the putative endogenous ligand responsible for slow oxidase.
本文描述了一种由CO₂/HCO₃⁻诱导产生的完全氧化型牛心细胞色素c氧化酶。这种形式的配体结合特性与Cl⁻连接的氧化酶相似[穆迪、库珀和里奇（1991年），《生物化学与生物物理学报》1059卷，第189 - 207页]。二者与氰化物的结合速率（在pH 6.5时为0.2 M⁻¹·s⁻¹）介于与该酶快速和慢速形式的结合速率之间，且二者与甲酸的结合几乎无法检测到。它们在与H₂O₂或在O₂存在下与CO的反应性较差方面也相似，而快速氧化酶与H₂O₂和CO反应分别会诱导形成“高铁血红素”和 “过氧” 状态。然而，这两种形式在近紫外/可见吸收光谱上存在明显差异；由CO₂/HCO₃⁻诱导产生的形式在427 nm处有一个Soret最大值，而Cl⁻连接的氧化酶在约424 nm处有一个与快速氧化酶相似的Soret最大值。似乎CO₂/HCO₃⁻和Cl⁻都是一类配体的成员，这类配体会降低双核中心的反应性，但不会阻碍分子内电子从血红素a转移到双核中心，这与负责慢速氧化酶的假定内源性配体不同。
