Han S W, Ching Y C, Rousseau D L
AT&T Bell Laboratories, Murray Hill, NJ 07974.
Proc Natl Acad Sci U S A. 1990 Apr;87(7):2491-5. doi: 10.1073/pnas.87.7.2491.
The primary intermediate in the reaction of oxygen with cytochrome c oxidase was generated by photodissociating carbon monoxide in a continuous flow rapid mixing apparatus. The presence of the primary intermediate was confirmed by a comparison of the iron-dioxygen stretching frequency with that obtained in the reaction of oxygen with the mixed-valence enzyme. For both of these preparations, the Fe-O2 stretching mode is detected at 568 cm-1, the same frequency as that found in oxyhemoglobin and oxymyoglobin. These data illustrate that the primary intermediate may be generated and detected at room temperature in the fully reduced enzyme and that the oxidation state of cytochrome a does not affect the structure of the iron-dioxygen complex. By following the changes in the intensity of the Fe-O2 stretching mode in the resonance Raman spectrum as a function of time, the first-order rate constant for the decay of the primary intermediate was found to be 3.5 x 10(4) s-1 (t1/2 = 20 microseconds).
在连续流动快速混合装置中,通过光解离一氧化碳生成了氧气与细胞色素c氧化酶反应的主要中间体。通过将铁-双氧伸缩频率与氧气与混合价态酶反应中获得的频率进行比较,证实了主要中间体的存在。对于这两种制剂,在568 cm-1处检测到Fe-O2伸缩模式,与在氧合血红蛋白和肌红蛋白中发现的频率相同。这些数据表明,主要中间体可以在室温下在完全还原的酶中产生和检测到,并且细胞色素a的氧化态不影响铁-双氧配合物的结构。通过跟踪共振拉曼光谱中Fe-O2伸缩模式强度随时间的变化,发现主要中间体衰变的一级速率常数为3.5×10(4) s-1(t1/2 = 20微秒)。