Cytochrome oxidase and its derivatives VI. The CO combining capacity of cytochrome c oxidase

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Summary

Ferrous cytochrome a3 is known to bind CO at pH 7.4, whereas cytochrome a does not do so. It is found that about one-half of the total haem a of cytochrome c oxidase (EC 1.9.3.1) is able to bind CO. This shows that the ratio of cytochrome a to cytochrome a3 is about 1. The validity of the method was established by showing that haemoglobin bound 1 mole of CO per mole of protohaem.

When cytochrome oxidase is kept at pH 10 at room temperature both cytochromes a and a3 are modified and both the modified cytochromes now react with CO. It is found that 1 mole of haem a of the modified oxidase binds approx. 1 mole of CO. This lends additional support to the result of the experiments with native cytochrome oxidase.

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