A phospholipid fraction from beef heart muscle which activates cytochrome c oxidase.

Cytochrome c oxidase has been found to be localized in a lipoprotein matrix in the mitochondrial membrane (l), which is undoubtedly responsible for the particulate nature of this enzyme when isolated from the tissue. Marinetti, Scaramuzzino, and Stotz (2) found that a purified cytochrome oxidase preparation contained 33% lipid which consisted of neutral fat, cholesterol, and phospholipids. The principal phospholipids found were phosphatidylcholine and phosphatidylethanolamine, as well as minor amounts of inositol phosphatide, phosphatidylserine, and sphingomyelin. Phospholipids have been reported to be very effective in reactivating various cytochrome c oxidase preparations. The purified “Preparation 2-4-1.5” of cytochrome c oxidase prepared by Greenlees and Wainio (3) required added phospholipids for activity, phosphatidylserine being the most effective. A 2% sodium deoxycholate extract of an insoluble heart musclepreparation was also found to reactivate the enzyme (4). Ambe ‘and Venkataraman (5) found phosphatidylinositol to be the most effective phospholipid activator of a depolymerized cytochrome oxidase preparation. Lysolecithin was reported by Igo et al. (6) to be the best activator of an acetone-extracted cytochrome oxidase preparation. This paper is concerned with the isolation and identification of a phospholipid component or components from bovine heart muscle which activate cytochrome c oxidase.