Reactions of cytochrome oxidase with oxygen and carbon monoxide

Although spectrophotometric determinations of steady states together with turnover rates have allowed 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 spectro- photometrically 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 ( Pre- liminary accounts of part of this work have been given by Gibson, Greenwood & Massey (1960) and by EXPERIMENTAL Cytochrome-oxida8e preparations. Two types were used: the venom preparation described by Greenwood (1963) (referred to below as the 'Greenwood preparation'), and the preparation of Yonetani (1960a As Emasol 4130, a product of the Kao Soap Co., Tokyo, could not be ob- tained, the preparation was stabilized with Tween 80 (L.Light and Co. Ltd.,Colnbrook, Bucks.), a poly(oxyethylene sorbitan mono-oleate).