REACTIONS OF CYTOCHROME OXIDASE WITH OXYGEN AND CARBON.
SHEFFIELD UNIV (ENGLAND) DEPT OF BIOCHEMISTRY
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The reaction of Yonetanis J. Biol. Chem v235 p845 1960 preparation of cytochrome oxidase with carbon monoxide is accurately second order with rate constant 80,000Msec at 20C and activation energy 6.4 kcal. The dissociation velocity constant of carbon monoxide is 0.023sec at 20C pH 7.4. One third of the total iron reacts with carbon monoxide to form the carbon monoxide compound as determined both by spectrophotometry and by gasometric methods. The reaction of oxygen with reduced cytochrome oxidase is rapid and the course of the reaction is complex. When the reaction between reduced cytochrome oxidase and oxygen is followed at different wavelengths, the course of reaction changes. These changes are attributed to consecutive reactions between oxygen and reduced cytochrome a3 and between reduced cytochrome a3 and oxidized cytochrome a. The spectrophotometric changes at different wavelengths may be reproduced using the extinction coefficients given by Yonetani.