Einarsdóttir O, Killough P M, Fee J A, Woodruff W H
University of California, Los Alamos National Laboratory, New Mexico 87545.
J Biol Chem. 1989 Feb 15;264(5):2405-8.
The C-O stretching frequencies of fully reduced carbonmonoxy cytochrome ba3, a newly discovered terminal oxidase of the bacterium Thermus thermophilus (Zimmermann, B.H., Nitsche, C.I., Fee, J.A., Rusnak, F., and Münck, E. (1988) Proc. Natl. Acad. Sci. U.S. A. 85, 5779-5783), are studied by Fourier transform infrared spectroscopy. Multiple C-O frequencies are observed in the Fourier transform infrared spectra, indicating the presence of discrete interconverting conformers of the enzyme. Upon photolysis, the CO is shown to migrate exclusively to CuB+. Above 200 K, the CO returns to the heme a3 by a thermal process which follows simple first-order kinetics. The rate of the reaction was studied from 205 to 230 K and at 300 K, yielding the activation parameters delta H = 14.9 kcal/mol and delta S = -5 cal/mol/K. These are compared with previously determined activation parameters for CO recombination in mitochondrial cytochrome aa3 preparations (Fiamingo, F.G., Altschuld, R.A., Moh, P.P., and Alben, J.O. (1982) J. Biol. Chem. 257, 1639-1650). We report the novel finding that CO remains bound to CuB+ at room temperature during continuous photolysis of cytochrome ba3, and we conjecture on the possible interference of copper-bound CO in "flow-flash" and "triple-trap" studies of cytochrome c oxidases.
利用傅里叶变换红外光谱法研究了嗜热栖热菌新发现的末端氧化酶——完全还原的一氧化碳细胞色素ba3的C-O伸缩频率。在傅里叶变换红外光谱中观察到多个C-O频率，表明该酶存在离散的相互转化构象体。光解后，CO被证明仅迁移至CuB+。在200 K以上，CO通过遵循简单一级动力学的热过程返回血红素a3。在205至230 K以及300 K下研究了该反应的速率，得到活化参数ΔH = 14.9 kcal/mol和ΔS = -5 cal/mol/K。将这些参数与先前测定的线粒体细胞色素aa3制剂中CO重组的活化参数进行了比较（Fiamingo, F.G., Altschuld, R.A., Moh, P.P., and Alben, J.O. (1982) J. Biol. Chem. 257, 1639 - 1650）。我们报告了一个新发现，即在细胞色素ba3的连续光解过程中，CO在室温下仍与CuB+结合，并且我们推测了铜结合的CO在细胞色素c氧化酶的“流动闪光”和“三重陷阱”研究中可能产生的干扰。
