PH dependent properties of chicken and beef cytochrome C oxidases

ABSTRACT

The pH dependent properties of mono-meric form of cytochrome c oxidases isolated from beef and chicken hearts tissue are described and compared with those of the enzyme dimer. Dimeric form of oxidase dissociated into Monemeric state of enzyme with increase of pH. The absorbtion spectra of alkaline incubated oxidase at pH 9.5 to pH 11.0 showed lambda Fe+2 maximum at 441 nm compared to 444 nm for typical dimeric oxidase at pH 7.4. The maxima for alpha Fe+2 are indicated at 604 nm for both neutral and alkaline incubated oxidase. The difference spectra [reduced-Co minus reduced] showed absorption maxima at 430 nm for alkaline incubated oxidase and 430 nm for dimeric oxidase. Carbon monoxide titration showed that alkaline incubated oxidase [at or above pH 10.5] reacted with approximately twice the amount of carbon monoxide compared to the oxidase at neutral pH of equal haem A contents. Titration of the purified monomers showed the reaction of carbon monoxide with only one of the two haem A contents of the oxidase similar to that of dimeric enzymes