Influence of non‐esterified fatty acids on respiratory control of reconstituted cytochrome‐ c oxidase

Bovine heart cytochrome‐ c oxidase was reconstituted in liposomes (asolectin) and the activity measured in the presence and absence of uncoupler at increasing concentrations of non‐esterified fatty acids. Palmitic and stearic acids resulted in a decrease of about 40% in the respiratory control ratio at a concentration of 1 νM, when measured using a spectrophotometric procedure but not with a polarographic assay method. At higher fatty acid concentrations no further change was found. A 50% decrease in respiratory control was determined when the enzyme was reconstituted in pure phosphatidylcholine containing 2% cardiolipin. The respiratory control of reconstituted cytochrome‐ c oxidase from bovine liver was not influenced by fatty acids.