Spectroscopic determination of cytochrome c oxidase content in tissues containing myoglobin or hemoglobin

A simple spectroscopic method for determining the cytochrome c oxidase, cytochrome a, a(3), content in tissue and mitochondria samples independent of myoglobin or blood contamination is described. Using tissue homogenates solubilized in Triton X-100, this assay relies on the selective reduction of mitochondrial cytochromes by the action of potassium cyanide. Monitoring the optical absorbance of these samples at 605 nm provided a quantitative determination of cytochrome c oxidase content in the presence of myoglobin or blood. The cytochrome c oxidase content of porcine heart mitochondria and whole tissue was determined to be 0.85 nmol/mg protein and 30.5 nmol/g wet wt, respectively. (C) 1996 Academic Press, Inc.