Reactions of cytochrome oxidase with oxygen and carbon monoxide.

Although spectrophotometric determinations of steady states together with turnover rates have allowed Chance (1952) to calculate that the rate of reaction of reduced cytochrome oxidase with oxygen must be about 107M-1 sec.-', no direct measurements of this rate appear to have been reported. This is due to the difficulty of obtaining the enzyme in a form which can be studied spectrophotometrically without the special double-beam methods of Chance (1951) for turbid preparations. In addition to the intrinsic interest of the rate measurements it was hoped that experiments with stoicheiometric quantities of enzyme and oxygen might help to resolve the vexed questions of the existence and function of cytochromes a and a3, and of the role of copper. Some of the experiments have been done with the venom-digest preparation of Greenwood (1963), but most have been carried out with the preparation of Yonetani (1960 a, 1961), which is stabilized by a non-ionic detergent. Preliminary accounts of part of this work have been given by Gibson, Greenwood & Massey (1960) and by Gibson & Greenwood (1962).