Photolytic activity of early intermediates in dioxygen activation and reduction by cytochrome oxidase
Photolytic activity of early intermediates in dioxygen activation and reduction by cytochrome oxidase
复制标题
细胞色素氧化酶活化和还原双氧过程中早期中间体的光解活性
DOI：
10.1021/ja00150a025
复制
发表时间：
1995
影响因子：
15
通讯作者：
G. Babcock
中科院分区：
文献类型：
--
作者：
C. Varotsis;G. Babcock
本文报道了室温下完全还原的（α ~（2+）As ~（2+））细胞色素氧化酶与分子氧反应的时间分辨共振拉曼光谱。我们监测了571 cm-1处的Fe 2 +-O2振动和反应光化性的时间过程。我们的研究结果表明，除了32+-O2物种，以下中间体的反应序列，这可以被描述为一个过氧物种，共有三个还原当量的双核中心，也是光不稳定的，可以光解再生的完全还原酶。我们观察到的光解活性衰减的表观速率常数为~ 104 s_1，这与在O2还原反应中观察到的其他弛豫现象相关。我们认为，这些现象的基本过程是与质子泵活性的酶的输入/输出构型转变。关于细胞色素/O2反应中早期中间体的光解活性的动力学的这些结果解决了我们的早期结果和对氧化酶/Ch反应时间过程的解释与Blackmore、Greenwood和吉布森的那些（J.Biol.Chem.1991，266，19245）之间的明显差异。我们还记录了拉曼光谱在低频（200-500 cm-1）区域在氧化酶/Oa反应，显示的r（Fe ~（2+）-his）伸缩振动的光产物，导致CO，O_2，和过氧加合物的光解。在O2还原反应过程中产生的光解产物具有与CO光解产物类似的振动性质，这表明血红素在配体光解后的弛豫动力学与配体无关.
Time-resolved resonance Raman spectra have been recorded during the reaction of fully reduced (a2+ as2+) cytochrome oxidase with dioxygen at room temperature. We have monitored the Fe2+—O2 vibration at 571 cm-1 and the time course of reaction photolability. Our results indicate that, in addition to the 32+—O2 species, the following intermediate in the reaction sequence, which can be described as a peroxy species with a total of three reducing equivalents in the binuclear center, is also photolabile and can be photolyzed to regenerate the fully reduced enzyme. The apparent rate constant that we observe for the decay of photolytic activity is~ 104 s_1, which correlates with other relaxation phenomena that have been observed in the O2 reduction reaction. We suggest that the underlying process that governs these phenomena is an input/output configurational transition associated with the proton-pumping activity of the enzyme. These results on the kinetics of the photolytic activity of the early intermediates in the cytochrome/02 reaction resolve apparent differences between our earlier results and interpretation of the oxidase/Ch reaction time course and those of Blackmore, Greenwood, and Gibson (J. Biol. Chem. 1991, 266, 19245). We have also recorded Raman spectra in the low-frequency (200—500 cm-1) region during the oxidase/Oa reaction that show the r (Fe2+—his) stretching vibration in photoproducts that result from CO, O2, and peroxy adduct photolysis. The photolysis products that can be generated during the O2 reduction reaction have vibrational properties similar to those of the CO photolysis product, which suggests that the relaxation dynamics of heme as following ligandphotolysis are independent of ligand.