Mechanistic Studies of Cytochrome c Oxidase = 사이트크롬산화요소의 메카니즘 연구

다국어 초록 (Multilingual Abstract)

Cytochrome c oxidase, the terminal enzyme in the electron transfer chain, catalyzes the reduction of oxygen to water in a multiple step process requiring four electrons. To study the mechanism of this process, the resonance Raman spectra of the intermediate states were measured during single turnover of the enzyme after catalytic initiation by photolysis of CO from the fully reduced preparation. By measuring the change in intensity of lines associated with cytochrome a, the electron transfer steps were determined and found to be biphasic with apparent rate constants of ~40 × 10^-3 s^-1 and ~1000 s^-1. The time dependence of the oxy, the ferryl, and the hydroxy intermediates could be accounted for by a simple reaction scheme which also accounts for the oxidation of cytochrome a and Cu_A. In this scheme the presence of the "peroxy" intermediate escapes detection because its decay rate is too fast in protoated solvent media. We confirm the presence of an oxygen isotope-sensitive line at 355 cm^-1. However, unlike the observations of Varotsis et al. [Proc. Natl, Acad. Sci, USA 90, 237-241 (1993)], who detect the line only at a reaction delay time of 160 us, we observe the line from 130 to 980 us, consisten with the recent observation of Ogura et al. [J. Am. Chem. Soc. 118, 5443-5449 (1996)] We postulate that the line at 355 cm^-1 is a bending mode of the ferryl intermediate..

목차 (Table of Contents)

• Abstract
• Introduction
• Materials and Methods
• Results
• Discussion
• Conclusions
• References