Role of phospholipids in cytochrome c oxidase activity.

Bile salts are commonly used in the isolation and purification of the lipid-rich respiratory enzymes. Wainio et al. (1, 2) found sodium deoxycholate to be particularly effective in the preparation of a soluble cytochrome c oxidase. Other workers have utilized sodium cholate (3). The use of both of these agents in the extraction of an insoluble heart muscle preparation made by the method of Keilin and Hartree has resulted in the isolation of an enzyme low in lipid and almost without cytochrome oxidase activity (4). Enzymatic activity was restored by the addition of various phospholipids. Hatefi (5) has also reported that a lipoprotein of mitochondrial origin, consisting of 9501, phospholipid is required for optimal activity of cytochrome c oxidase. More recently Igo et al. have shown (6) that a cytochrome c oxidase preparation was reactivated by the addition of surface active agents and that enzymatic activity could be correlated with the phospholipid content of the enzyme.